Vulnerability-Lookup

URL	Tags
https://github.com/Kludex/python-multipart/securi…	x_refsource_CONFIRM

Vendor	Product	Version	CPE status
Kludex	python-multipart	Affected: < 0.0.30	guessed

BREW-CYCODE-CVE-2026-53537 (GHSA-VFFW-93WF-4J4Q)

Vulnerability from osv_homebrew – Published: 2026-08-13 16:42 – Updated: 2026-09-17 18:32 – Source website

Summary

python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters

Details

Summary

parse_options_header parsed Content-Disposition (and Content-Type) headers with email.message.Message, which transparently applies RFC 2231/5987 decoding. The extended parameter syntax (filename*=charset'lang'value, name*=..., and the filename*0/filename*1 continuation form) is decoded and surfaced under the bare filename/name key, and overrides the plain parameter when both are present. RFC 7578 §4.2 explicitly forbids the filename* form in multipart/form-data.

Components that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for multipart/form-data (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.

Details

Given both a plain and an extended parameter, the extended value won. For example:

Content-Disposition: form-data; name="comment"; name*=utf-8''role

An inspector following RFC 7578 sees the field comment, while the returned value was name=role. The same applies to filenames:

Content-Disposition: form-data; name="upload"; filename="safe.txt"; filename*=utf-8''evil.php

The inspector sees safe.txt, while the returned value was filename=evil.php. Continuation parameters (filename*0, filename*1, and so on) were likewise reassembled into a filename invisible to a plain filename= match, and percent encoded sequences in the extended value were decoded (so ..%2F, %00, and similar appeared in the returned filename).

This affects the high level parse_options_header, FormParser, create_form_parser, and parse_form APIs, and reaches Starlette/FastAPI through request.form(), where the smuggled value is exposed as the form field name or UploadFile.filename.

Impact

This is an interpretation conflict (CWE-436) with other multipart/form-data parsers. An attacker able to submit multipart/form-data can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded ..%2F sequences. Decoded control bytes such as %00 can likewise cause confusion between an upstream validator and the backend. The File class applies os.path.basename, so file writing through it is not directly affected.

Mitigation

Upgrade to python-multipart 0.0.30 or later, which ignores RFC 2231/5987 extended parameters (name*, filename*, and their continuations) so the plain name/filename parameter remains authoritative. RFC 7578 §4.2 forbids filename* for multipart/form-data; name* and the continuation forms are dropped for the same reason, since they are not valid multipart/form-data parameters either.

Severity

3.7 (Low)


                    
                      CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

References

URL

Type

	https://github.com/Kludex/python-multipart/securi…	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-53537	ADVISORY
	https://github.com/Kludex/python-multipart	PACKAGE
	https://github.com/advisories/GHSA-vffw-93wf-4j4q	ADVISORY
	https://github.com/pypa/advisory-database/blob/ma…	WEB
	https://pypi.org/project/python-multipart	WEB

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "python-multipart",
        "resource_purl": "pkg:pypi/python-multipart@0.0.32",
        "upstream_fixed_in": "0.0.30"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "cycode",
        "purl": "pkg:brew/cycode"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.2.0"
            },
            {
              "fixed": "3.16.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/python-multipart@0.0.32",
        "name": "python-multipart",
        "resource": "python-multipart",
        "strategy": "registry",
        "subject_version": "0.0.32"
      }
    ]
  },
  "details": "### Summary\n\n`parse_options_header` parsed `Content-Disposition` (and `Content-Type`) headers with [`email.message.Message`](https://docs.python.org/3/library/email.compat32-message.html#email.message.Message), which transparently applies [RFC 2231](https://datatracker.ietf.org/doc/html/rfc2231)/[5987](https://datatracker.ietf.org/doc/html/rfc5987) decoding. The extended parameter syntax (`filename*=charset\u0027lang\u0027value`, `name*=...`, and the `filename*0`/`filename*1` continuation form) is decoded and surfaced under the bare `filename`/`name` key, and overrides the plain parameter when both are present. [RFC 7578 \u00a74.2](https://datatracker.ietf.org/doc/html/rfc7578#section-4.2) explicitly forbids the `filename*` form in `multipart/form-data`.\n\nComponents that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for `multipart/form-data` (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.\n\n### Details\n\nGiven both a plain and an extended parameter, the extended value won. For example:\n\n```\nContent-Disposition: form-data; name=\"comment\"; name*=utf-8\u0027\u0027role\n```\n\nAn inspector following RFC 7578 sees the field `comment`, while the returned value was `name=role`. The same applies to filenames:\n\n```\nContent-Disposition: form-data; name=\"upload\"; filename=\"safe.txt\"; filename*=utf-8\u0027\u0027evil.php\n```\n\nThe inspector sees `safe.txt`, while the returned value was `filename=evil.php`. Continuation parameters (`filename*0`, `filename*1`, and so on) were likewise reassembled into a `filename` invisible to a plain `filename=` match, and percent encoded sequences in the extended value were decoded (so `..%2F`, `%00`, and similar appeared in the returned filename).\n\nThis affects the high level `parse_options_header`, `FormParser`, `create_form_parser`, and `parse_form` APIs, and reaches Starlette/FastAPI through `request.form()`, where the smuggled value is exposed as the form field name or [`UploadFile.filename`](https://www.starlette.io/requests/#request-files).\n\n### Impact\n\nThis is an interpretation conflict ([CWE-436](https://cwe.mitre.org/data/definitions/436.html)) with other `multipart/form-data` parsers. An attacker able to submit `multipart/form-data` can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded `..%2F` sequences. Decoded control bytes such as `%00` can likewise cause confusion between an upstream validator and the backend. The `File` class applies `os.path.basename`, so file writing through it is not directly affected.\n\n### Mitigation\n\nUpgrade to `python-multipart` `0.0.30` or later, which ignores RFC 2231/5987 extended parameters (`name*`, `filename*`, and their continuations) so the plain `name`/`filename` parameter remains authoritative. RFC 7578 \u00a74.2 forbids `filename*` for `multipart/form-data`; `name*` and the continuation forms are dropped for the same reason, since they are not valid `multipart/form-data` parameters either.",
  "id": "BREW-cycode-CVE-2026-53537",
  "modified": "2026-09-17T18:32:20Z",
  "published": "2026-08-13T16:42:07Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53537"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Kludex/python-multipart"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/blob/main/vulns/python-multipart/PYSEC-2026-3041.yaml"
    },
    {
      "type": "WEB",
      "url": "https://pypi.org/project/python-multipart"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters",
  "upstream": [
    "GHSA-vffw-93wf-4j4q",
    "CVE-2026-53537",
    "PYSEC-2026-3041"
  ]
}

BREW-DATASETTE-CVE-2026-53537 (GHSA-VFFW-93WF-4J4Q)

Vulnerability from osv_homebrew – Published: 2026-08-13 16:42 – Updated: 2026-09-17 17:44 – Source website

Summary

python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters

Details

Summary

parse_options_header parsed Content-Disposition (and Content-Type) headers with email.message.Message, which transparently applies RFC 2231/5987 decoding. The extended parameter syntax (filename*=charset'lang'value, name*=..., and the filename*0/filename*1 continuation form) is decoded and surfaced under the bare filename/name key, and overrides the plain parameter when both are present. RFC 7578 §4.2 explicitly forbids the filename* form in multipart/form-data.

Components that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for multipart/form-data (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.

Details

Given both a plain and an extended parameter, the extended value won. For example:

Content-Disposition: form-data; name="comment"; name*=utf-8''role

An inspector following RFC 7578 sees the field comment, while the returned value was name=role. The same applies to filenames:

Content-Disposition: form-data; name="upload"; filename="safe.txt"; filename*=utf-8''evil.php

The inspector sees safe.txt, while the returned value was filename=evil.php. Continuation parameters (filename*0, filename*1, and so on) were likewise reassembled into a filename invisible to a plain filename= match, and percent encoded sequences in the extended value were decoded (so ..%2F, %00, and similar appeared in the returned filename).

This affects the high level parse_options_header, FormParser, create_form_parser, and parse_form APIs, and reaches Starlette/FastAPI through request.form(), where the smuggled value is exposed as the form field name or UploadFile.filename.

Impact

This is an interpretation conflict (CWE-436) with other multipart/form-data parsers. An attacker able to submit multipart/form-data can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded ..%2F sequences. Decoded control bytes such as %00 can likewise cause confusion between an upstream validator and the backend. The File class applies os.path.basename, so file writing through it is not directly affected.

Mitigation

Upgrade to python-multipart 0.0.30 or later, which ignores RFC 2231/5987 extended parameters (name*, filename*, and their continuations) so the plain name/filename parameter remains authoritative. RFC 7578 §4.2 forbids filename* for multipart/form-data; name* and the continuation forms are dropped for the same reason, since they are not valid multipart/form-data parameters either.

Severity

3.7 (Low)


                    
                      CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

References

URL

Type

	https://github.com/Kludex/python-multipart/securi…	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-53537	ADVISORY
	https://github.com/Kludex/python-multipart	PACKAGE
	https://github.com/advisories/GHSA-vffw-93wf-4j4q	ADVISORY
	https://github.com/pypa/advisory-database/blob/ma…	WEB
	https://pypi.org/project/python-multipart	WEB

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "python-multipart",
        "resource_purl": "pkg:pypi/python-multipart@0.0.32",
        "upstream_fixed_in": "0.0.30"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "datasette",
        "purl": "pkg:brew/datasette"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.47.3"
            },
            {
              "fixed": "0.65.2_5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/python-multipart@0.0.32",
        "name": "python-multipart",
        "resource": "python-multipart",
        "strategy": "registry",
        "subject_version": "0.0.32"
      }
    ]
  },
  "details": "### Summary\n\n`parse_options_header` parsed `Content-Disposition` (and `Content-Type`) headers with [`email.message.Message`](https://docs.python.org/3/library/email.compat32-message.html#email.message.Message), which transparently applies [RFC 2231](https://datatracker.ietf.org/doc/html/rfc2231)/[5987](https://datatracker.ietf.org/doc/html/rfc5987) decoding. The extended parameter syntax (`filename*=charset\u0027lang\u0027value`, `name*=...`, and the `filename*0`/`filename*1` continuation form) is decoded and surfaced under the bare `filename`/`name` key, and overrides the plain parameter when both are present. [RFC 7578 \u00a74.2](https://datatracker.ietf.org/doc/html/rfc7578#section-4.2) explicitly forbids the `filename*` form in `multipart/form-data`.\n\nComponents that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for `multipart/form-data` (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.\n\n### Details\n\nGiven both a plain and an extended parameter, the extended value won. For example:\n\n```\nContent-Disposition: form-data; name=\"comment\"; name*=utf-8\u0027\u0027role\n```\n\nAn inspector following RFC 7578 sees the field `comment`, while the returned value was `name=role`. The same applies to filenames:\n\n```\nContent-Disposition: form-data; name=\"upload\"; filename=\"safe.txt\"; filename*=utf-8\u0027\u0027evil.php\n```\n\nThe inspector sees `safe.txt`, while the returned value was `filename=evil.php`. Continuation parameters (`filename*0`, `filename*1`, and so on) were likewise reassembled into a `filename` invisible to a plain `filename=` match, and percent encoded sequences in the extended value were decoded (so `..%2F`, `%00`, and similar appeared in the returned filename).\n\nThis affects the high level `parse_options_header`, `FormParser`, `create_form_parser`, and `parse_form` APIs, and reaches Starlette/FastAPI through `request.form()`, where the smuggled value is exposed as the form field name or [`UploadFile.filename`](https://www.starlette.io/requests/#request-files).\n\n### Impact\n\nThis is an interpretation conflict ([CWE-436](https://cwe.mitre.org/data/definitions/436.html)) with other `multipart/form-data` parsers. An attacker able to submit `multipart/form-data` can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded `..%2F` sequences. Decoded control bytes such as `%00` can likewise cause confusion between an upstream validator and the backend. The `File` class applies `os.path.basename`, so file writing through it is not directly affected.\n\n### Mitigation\n\nUpgrade to `python-multipart` `0.0.30` or later, which ignores RFC 2231/5987 extended parameters (`name*`, `filename*`, and their continuations) so the plain `name`/`filename` parameter remains authoritative. RFC 7578 \u00a74.2 forbids `filename*` for `multipart/form-data`; `name*` and the continuation forms are dropped for the same reason, since they are not valid `multipart/form-data` parameters either.",
  "id": "BREW-datasette-CVE-2026-53537",
  "modified": "2026-09-17T17:44:18Z",
  "published": "2026-08-13T16:42:09Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53537"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Kludex/python-multipart"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/blob/main/vulns/python-multipart/PYSEC-2026-3041.yaml"
    },
    {
      "type": "WEB",
      "url": "https://pypi.org/project/python-multipart"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters",
  "upstream": [
    "GHSA-vffw-93wf-4j4q",
    "CVE-2026-53537",
    "PYSEC-2026-3041"
  ]
}

BREW-DSTACK-CVE-2026-53537 (GHSA-VFFW-93WF-4J4Q)

Vulnerability from osv_homebrew – Published: 2026-08-13 16:43 – Updated: 2026-09-17 18:14 – Source website

Summary

python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters

Details

Summary

parse_options_header parsed Content-Disposition (and Content-Type) headers with email.message.Message, which transparently applies RFC 2231/5987 decoding. The extended parameter syntax (filename*=charset'lang'value, name*=..., and the filename*0/filename*1 continuation form) is decoded and surfaced under the bare filename/name key, and overrides the plain parameter when both are present. RFC 7578 §4.2 explicitly forbids the filename* form in multipart/form-data.

Components that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for multipart/form-data (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.

Details

Given both a plain and an extended parameter, the extended value won. For example:

Content-Disposition: form-data; name="comment"; name*=utf-8''role

An inspector following RFC 7578 sees the field comment, while the returned value was name=role. The same applies to filenames:

Content-Disposition: form-data; name="upload"; filename="safe.txt"; filename*=utf-8''evil.php

The inspector sees safe.txt, while the returned value was filename=evil.php. Continuation parameters (filename*0, filename*1, and so on) were likewise reassembled into a filename invisible to a plain filename= match, and percent encoded sequences in the extended value were decoded (so ..%2F, %00, and similar appeared in the returned filename).

This affects the high level parse_options_header, FormParser, create_form_parser, and parse_form APIs, and reaches Starlette/FastAPI through request.form(), where the smuggled value is exposed as the form field name or UploadFile.filename.

Impact

This is an interpretation conflict (CWE-436) with other multipart/form-data parsers. An attacker able to submit multipart/form-data can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded ..%2F sequences. Decoded control bytes such as %00 can likewise cause confusion between an upstream validator and the backend. The File class applies os.path.basename, so file writing through it is not directly affected.

Mitigation

Upgrade to python-multipart 0.0.30 or later, which ignores RFC 2231/5987 extended parameters (name*, filename*, and their continuations) so the plain name/filename parameter remains authoritative. RFC 7578 §4.2 forbids filename* for multipart/form-data; name* and the continuation forms are dropped for the same reason, since they are not valid multipart/form-data parameters either.

Severity

3.7 (Low)


                    
                      CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

References

URL

Type

	https://github.com/Kludex/python-multipart/securi…	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-53537	ADVISORY
	https://github.com/Kludex/python-multipart	PACKAGE
	https://github.com/advisories/GHSA-vffw-93wf-4j4q	ADVISORY
	https://github.com/pypa/advisory-database/blob/ma…	WEB
	https://pypi.org/project/python-multipart	WEB

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "python-multipart",
        "resource_purl": "pkg:pypi/python-multipart@0.0.32",
        "upstream_fixed_in": "0.0.30"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "dstack",
        "purl": "pkg:brew/dstack"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.12.1"
            },
            {
              "fixed": "0.20.23"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/python-multipart@0.0.32",
        "name": "python-multipart",
        "resource": "python-multipart",
        "strategy": "registry",
        "subject_version": "0.0.32"
      }
    ]
  },
  "details": "### Summary\n\n`parse_options_header` parsed `Content-Disposition` (and `Content-Type`) headers with [`email.message.Message`](https://docs.python.org/3/library/email.compat32-message.html#email.message.Message), which transparently applies [RFC 2231](https://datatracker.ietf.org/doc/html/rfc2231)/[5987](https://datatracker.ietf.org/doc/html/rfc5987) decoding. The extended parameter syntax (`filename*=charset\u0027lang\u0027value`, `name*=...`, and the `filename*0`/`filename*1` continuation form) is decoded and surfaced under the bare `filename`/`name` key, and overrides the plain parameter when both are present. [RFC 7578 \u00a74.2](https://datatracker.ietf.org/doc/html/rfc7578#section-4.2) explicitly forbids the `filename*` form in `multipart/form-data`.\n\nComponents that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for `multipart/form-data` (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.\n\n### Details\n\nGiven both a plain and an extended parameter, the extended value won. For example:\n\n```\nContent-Disposition: form-data; name=\"comment\"; name*=utf-8\u0027\u0027role\n```\n\nAn inspector following RFC 7578 sees the field `comment`, while the returned value was `name=role`. The same applies to filenames:\n\n```\nContent-Disposition: form-data; name=\"upload\"; filename=\"safe.txt\"; filename*=utf-8\u0027\u0027evil.php\n```\n\nThe inspector sees `safe.txt`, while the returned value was `filename=evil.php`. Continuation parameters (`filename*0`, `filename*1`, and so on) were likewise reassembled into a `filename` invisible to a plain `filename=` match, and percent encoded sequences in the extended value were decoded (so `..%2F`, `%00`, and similar appeared in the returned filename).\n\nThis affects the high level `parse_options_header`, `FormParser`, `create_form_parser`, and `parse_form` APIs, and reaches Starlette/FastAPI through `request.form()`, where the smuggled value is exposed as the form field name or [`UploadFile.filename`](https://www.starlette.io/requests/#request-files).\n\n### Impact\n\nThis is an interpretation conflict ([CWE-436](https://cwe.mitre.org/data/definitions/436.html)) with other `multipart/form-data` parsers. An attacker able to submit `multipart/form-data` can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded `..%2F` sequences. Decoded control bytes such as `%00` can likewise cause confusion between an upstream validator and the backend. The `File` class applies `os.path.basename`, so file writing through it is not directly affected.\n\n### Mitigation\n\nUpgrade to `python-multipart` `0.0.30` or later, which ignores RFC 2231/5987 extended parameters (`name*`, `filename*`, and their continuations) so the plain `name`/`filename` parameter remains authoritative. RFC 7578 \u00a74.2 forbids `filename*` for `multipart/form-data`; `name*` and the continuation forms are dropped for the same reason, since they are not valid `multipart/form-data` parameters either.",
  "id": "BREW-dstack-CVE-2026-53537",
  "modified": "2026-09-17T18:14:18Z",
  "published": "2026-08-13T16:43:57Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53537"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Kludex/python-multipart"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/blob/main/vulns/python-multipart/PYSEC-2026-3041.yaml"
    },
    {
      "type": "WEB",
      "url": "https://pypi.org/project/python-multipart"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters",
  "upstream": [
    "GHSA-vffw-93wf-4j4q",
    "CVE-2026-53537",
    "PYSEC-2026-3041"
  ]
}

BREW-FASTAPI-CVE-2026-53537 (GHSA-VFFW-93WF-4J4Q)

Vulnerability from osv_homebrew – Published: 2026-08-13 16:46 – Updated: 2026-09-17 19:08 – Source website

Summary

python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters

Details

Summary

parse_options_header parsed Content-Disposition (and Content-Type) headers with email.message.Message, which transparently applies RFC 2231/5987 decoding. The extended parameter syntax (filename*=charset'lang'value, name*=..., and the filename*0/filename*1 continuation form) is decoded and surfaced under the bare filename/name key, and overrides the plain parameter when both are present. RFC 7578 §4.2 explicitly forbids the filename* form in multipart/form-data.

Components that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for multipart/form-data (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.

Details

Given both a plain and an extended parameter, the extended value won. For example:

Content-Disposition: form-data; name="comment"; name*=utf-8''role

An inspector following RFC 7578 sees the field comment, while the returned value was name=role. The same applies to filenames:

Content-Disposition: form-data; name="upload"; filename="safe.txt"; filename*=utf-8''evil.php

The inspector sees safe.txt, while the returned value was filename=evil.php. Continuation parameters (filename*0, filename*1, and so on) were likewise reassembled into a filename invisible to a plain filename= match, and percent encoded sequences in the extended value were decoded (so ..%2F, %00, and similar appeared in the returned filename).

This affects the high level parse_options_header, FormParser, create_form_parser, and parse_form APIs, and reaches Starlette/FastAPI through request.form(), where the smuggled value is exposed as the form field name or UploadFile.filename.

Impact

This is an interpretation conflict (CWE-436) with other multipart/form-data parsers. An attacker able to submit multipart/form-data can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded ..%2F sequences. Decoded control bytes such as %00 can likewise cause confusion between an upstream validator and the backend. The File class applies os.path.basename, so file writing through it is not directly affected.

Mitigation

Upgrade to python-multipart 0.0.30 or later, which ignores RFC 2231/5987 extended parameters (name*, filename*, and their continuations) so the plain name/filename parameter remains authoritative. RFC 7578 §4.2 forbids filename* for multipart/form-data; name* and the continuation forms are dropped for the same reason, since they are not valid multipart/form-data parameters either.

Severity

3.7 (Low)


                    
                      CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

References

URL

Type

	https://github.com/Kludex/python-multipart/securi…	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-53537	ADVISORY
	https://github.com/Kludex/python-multipart	PACKAGE
	https://github.com/advisories/GHSA-vffw-93wf-4j4q	ADVISORY
	https://github.com/pypa/advisory-database/blob/ma…	WEB
	https://pypi.org/project/python-multipart	WEB

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "python-multipart",
        "resource_purl": "pkg:pypi/python-multipart@0.0.32",
        "upstream_fixed_in": "0.0.30"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "fastapi",
        "purl": "pkg:brew/fastapi"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.111.0"
            },
            {
              "fixed": "0.137.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/python-multipart@0.0.32",
        "name": "python-multipart",
        "resource": "python-multipart",
        "strategy": "registry",
        "subject_version": "0.0.32"
      }
    ]
  },
  "details": "### Summary\n\n`parse_options_header` parsed `Content-Disposition` (and `Content-Type`) headers with [`email.message.Message`](https://docs.python.org/3/library/email.compat32-message.html#email.message.Message), which transparently applies [RFC 2231](https://datatracker.ietf.org/doc/html/rfc2231)/[5987](https://datatracker.ietf.org/doc/html/rfc5987) decoding. The extended parameter syntax (`filename*=charset\u0027lang\u0027value`, `name*=...`, and the `filename*0`/`filename*1` continuation form) is decoded and surfaced under the bare `filename`/`name` key, and overrides the plain parameter when both are present. [RFC 7578 \u00a74.2](https://datatracker.ietf.org/doc/html/rfc7578#section-4.2) explicitly forbids the `filename*` form in `multipart/form-data`.\n\nComponents that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for `multipart/form-data` (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.\n\n### Details\n\nGiven both a plain and an extended parameter, the extended value won. For example:\n\n```\nContent-Disposition: form-data; name=\"comment\"; name*=utf-8\u0027\u0027role\n```\n\nAn inspector following RFC 7578 sees the field `comment`, while the returned value was `name=role`. The same applies to filenames:\n\n```\nContent-Disposition: form-data; name=\"upload\"; filename=\"safe.txt\"; filename*=utf-8\u0027\u0027evil.php\n```\n\nThe inspector sees `safe.txt`, while the returned value was `filename=evil.php`. Continuation parameters (`filename*0`, `filename*1`, and so on) were likewise reassembled into a `filename` invisible to a plain `filename=` match, and percent encoded sequences in the extended value were decoded (so `..%2F`, `%00`, and similar appeared in the returned filename).\n\nThis affects the high level `parse_options_header`, `FormParser`, `create_form_parser`, and `parse_form` APIs, and reaches Starlette/FastAPI through `request.form()`, where the smuggled value is exposed as the form field name or [`UploadFile.filename`](https://www.starlette.io/requests/#request-files).\n\n### Impact\n\nThis is an interpretation conflict ([CWE-436](https://cwe.mitre.org/data/definitions/436.html)) with other `multipart/form-data` parsers. An attacker able to submit `multipart/form-data` can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded `..%2F` sequences. Decoded control bytes such as `%00` can likewise cause confusion between an upstream validator and the backend. The `File` class applies `os.path.basename`, so file writing through it is not directly affected.\n\n### Mitigation\n\nUpgrade to `python-multipart` `0.0.30` or later, which ignores RFC 2231/5987 extended parameters (`name*`, `filename*`, and their continuations) so the plain `name`/`filename` parameter remains authoritative. RFC 7578 \u00a74.2 forbids `filename*` for `multipart/form-data`; `name*` and the continuation forms are dropped for the same reason, since they are not valid `multipart/form-data` parameters either.",
  "id": "BREW-fastapi-CVE-2026-53537",
  "modified": "2026-09-17T19:08:32Z",
  "published": "2026-08-13T16:46:30Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53537"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Kludex/python-multipart"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/blob/main/vulns/python-multipart/PYSEC-2026-3041.yaml"
    },
    {
      "type": "WEB",
      "url": "https://pypi.org/project/python-multipart"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters",
  "upstream": [
    "GHSA-vffw-93wf-4j4q",
    "CVE-2026-53537",
    "PYSEC-2026-3041"
  ]
}

BREW-FASTMCP-CVE-2026-53537 (GHSA-VFFW-93WF-4J4Q)

Vulnerability from osv_homebrew – Published: 2026-08-13 16:46 – Updated: 2026-09-17 19:27 – Source website

Summary

python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters

Details

Summary

parse_options_header parsed Content-Disposition (and Content-Type) headers with email.message.Message, which transparently applies RFC 2231/5987 decoding. The extended parameter syntax (filename*=charset'lang'value, name*=..., and the filename*0/filename*1 continuation form) is decoded and surfaced under the bare filename/name key, and overrides the plain parameter when both are present. RFC 7578 §4.2 explicitly forbids the filename* form in multipart/form-data.

Components that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for multipart/form-data (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.

Details

Given both a plain and an extended parameter, the extended value won. For example:

Content-Disposition: form-data; name="comment"; name*=utf-8''role

An inspector following RFC 7578 sees the field comment, while the returned value was name=role. The same applies to filenames:

Content-Disposition: form-data; name="upload"; filename="safe.txt"; filename*=utf-8''evil.php

The inspector sees safe.txt, while the returned value was filename=evil.php. Continuation parameters (filename*0, filename*1, and so on) were likewise reassembled into a filename invisible to a plain filename= match, and percent encoded sequences in the extended value were decoded (so ..%2F, %00, and similar appeared in the returned filename).

This affects the high level parse_options_header, FormParser, create_form_parser, and parse_form APIs, and reaches Starlette/FastAPI through request.form(), where the smuggled value is exposed as the form field name or UploadFile.filename.

Impact

This is an interpretation conflict (CWE-436) with other multipart/form-data parsers. An attacker able to submit multipart/form-data can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded ..%2F sequences. Decoded control bytes such as %00 can likewise cause confusion between an upstream validator and the backend. The File class applies os.path.basename, so file writing through it is not directly affected.

Mitigation

Upgrade to python-multipart 0.0.30 or later, which ignores RFC 2231/5987 extended parameters (name*, filename*, and their continuations) so the plain name/filename parameter remains authoritative. RFC 7578 §4.2 forbids filename* for multipart/form-data; name* and the continuation forms are dropped for the same reason, since they are not valid multipart/form-data parameters either.

Severity

3.7 (Low)


                    
                      CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

References

URL

Type

	https://github.com/Kludex/python-multipart/securi…	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-53537	ADVISORY
	https://github.com/Kludex/python-multipart	PACKAGE
	https://github.com/advisories/GHSA-vffw-93wf-4j4q	ADVISORY
	https://github.com/pypa/advisory-database/blob/ma…	WEB
	https://pypi.org/project/python-multipart	WEB

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "python-multipart",
        "resource_purl": "pkg:pypi/python-multipart@0.0.32",
        "upstream_fixed_in": "0.0.30"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "fastmcp",
        "purl": "pkg:brew/fastmcp"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.12.3"
            },
            {
              "fixed": "3.4.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/python-multipart@0.0.32",
        "name": "python-multipart",
        "resource": "python-multipart",
        "strategy": "registry",
        "subject_version": "0.0.32"
      }
    ]
  },
  "details": "### Summary\n\n`parse_options_header` parsed `Content-Disposition` (and `Content-Type`) headers with [`email.message.Message`](https://docs.python.org/3/library/email.compat32-message.html#email.message.Message), which transparently applies [RFC 2231](https://datatracker.ietf.org/doc/html/rfc2231)/[5987](https://datatracker.ietf.org/doc/html/rfc5987) decoding. The extended parameter syntax (`filename*=charset\u0027lang\u0027value`, `name*=...`, and the `filename*0`/`filename*1` continuation form) is decoded and surfaced under the bare `filename`/`name` key, and overrides the plain parameter when both are present. [RFC 7578 \u00a74.2](https://datatracker.ietf.org/doc/html/rfc7578#section-4.2) explicitly forbids the `filename*` form in `multipart/form-data`.\n\nComponents that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for `multipart/form-data` (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.\n\n### Details\n\nGiven both a plain and an extended parameter, the extended value won. For example:\n\n```\nContent-Disposition: form-data; name=\"comment\"; name*=utf-8\u0027\u0027role\n```\n\nAn inspector following RFC 7578 sees the field `comment`, while the returned value was `name=role`. The same applies to filenames:\n\n```\nContent-Disposition: form-data; name=\"upload\"; filename=\"safe.txt\"; filename*=utf-8\u0027\u0027evil.php\n```\n\nThe inspector sees `safe.txt`, while the returned value was `filename=evil.php`. Continuation parameters (`filename*0`, `filename*1`, and so on) were likewise reassembled into a `filename` invisible to a plain `filename=` match, and percent encoded sequences in the extended value were decoded (so `..%2F`, `%00`, and similar appeared in the returned filename).\n\nThis affects the high level `parse_options_header`, `FormParser`, `create_form_parser`, and `parse_form` APIs, and reaches Starlette/FastAPI through `request.form()`, where the smuggled value is exposed as the form field name or [`UploadFile.filename`](https://www.starlette.io/requests/#request-files).\n\n### Impact\n\nThis is an interpretation conflict ([CWE-436](https://cwe.mitre.org/data/definitions/436.html)) with other `multipart/form-data` parsers. An attacker able to submit `multipart/form-data` can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded `..%2F` sequences. Decoded control bytes such as `%00` can likewise cause confusion between an upstream validator and the backend. The `File` class applies `os.path.basename`, so file writing through it is not directly affected.\n\n### Mitigation\n\nUpgrade to `python-multipart` `0.0.30` or later, which ignores RFC 2231/5987 extended parameters (`name*`, `filename*`, and their continuations) so the plain `name`/`filename` parameter remains authoritative. RFC 7578 \u00a74.2 forbids `filename*` for `multipart/form-data`; `name*` and the continuation forms are dropped for the same reason, since they are not valid `multipart/form-data` parameters either.",
  "id": "BREW-fastmcp-CVE-2026-53537",
  "modified": "2026-09-17T19:27:54Z",
  "published": "2026-08-13T16:46:31Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53537"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Kludex/python-multipart"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/blob/main/vulns/python-multipart/PYSEC-2026-3041.yaml"
    },
    {
      "type": "WEB",
      "url": "https://pypi.org/project/python-multipart"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters",
  "upstream": [
    "GHSA-vffw-93wf-4j4q",
    "CVE-2026-53537",
    "PYSEC-2026-3041"
  ]
}

BREW-GPTME-CVE-2026-53537 (GHSA-VFFW-93WF-4J4Q)

Vulnerability from osv_homebrew – Published: 2026-08-13 16:54 – Updated: 2026-09-17 18:12 – Source website

Summary

python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters

Details

Summary

parse_options_header parsed Content-Disposition (and Content-Type) headers with email.message.Message, which transparently applies RFC 2231/5987 decoding. The extended parameter syntax (filename*=charset'lang'value, name*=..., and the filename*0/filename*1 continuation form) is decoded and surfaced under the bare filename/name key, and overrides the plain parameter when both are present. RFC 7578 §4.2 explicitly forbids the filename* form in multipart/form-data.

Components that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for multipart/form-data (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.

Details

Given both a plain and an extended parameter, the extended value won. For example:

Content-Disposition: form-data; name="comment"; name*=utf-8''role

An inspector following RFC 7578 sees the field comment, while the returned value was name=role. The same applies to filenames:

Content-Disposition: form-data; name="upload"; filename="safe.txt"; filename*=utf-8''evil.php

The inspector sees safe.txt, while the returned value was filename=evil.php. Continuation parameters (filename*0, filename*1, and so on) were likewise reassembled into a filename invisible to a plain filename= match, and percent encoded sequences in the extended value were decoded (so ..%2F, %00, and similar appeared in the returned filename).

This affects the high level parse_options_header, FormParser, create_form_parser, and parse_form APIs, and reaches Starlette/FastAPI through request.form(), where the smuggled value is exposed as the form field name or UploadFile.filename.

Impact

This is an interpretation conflict (CWE-436) with other multipart/form-data parsers. An attacker able to submit multipart/form-data can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded ..%2F sequences. Decoded control bytes such as %00 can likewise cause confusion between an upstream validator and the backend. The File class applies os.path.basename, so file writing through it is not directly affected.

Mitigation

Upgrade to python-multipart 0.0.30 or later, which ignores RFC 2231/5987 extended parameters (name*, filename*, and their continuations) so the plain name/filename parameter remains authoritative. RFC 7578 §4.2 forbids filename* for multipart/form-data; name* and the continuation forms are dropped for the same reason, since they are not valid multipart/form-data parameters either.

Severity

3.7 (Low)


                    
                      CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

References

URL

Type

	https://github.com/Kludex/python-multipart/securi…	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-53537	ADVISORY
	https://github.com/Kludex/python-multipart	PACKAGE
	https://github.com/advisories/GHSA-vffw-93wf-4j4q	ADVISORY
	https://github.com/pypa/advisory-database/blob/ma…	WEB
	https://pypi.org/project/python-multipart	WEB

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "python-multipart",
        "resource_purl": "pkg:pypi/python-multipart@0.0.32",
        "upstream_fixed_in": "0.0.30"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "gptme",
        "purl": "pkg:brew/gptme"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.28.0"
            },
            {
              "fixed": "0.31.0_12"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/python-multipart@0.0.32",
        "name": "python-multipart",
        "resource": "python-multipart",
        "strategy": "registry",
        "subject_version": "0.0.32"
      }
    ]
  },
  "details": "### Summary\n\n`parse_options_header` parsed `Content-Disposition` (and `Content-Type`) headers with [`email.message.Message`](https://docs.python.org/3/library/email.compat32-message.html#email.message.Message), which transparently applies [RFC 2231](https://datatracker.ietf.org/doc/html/rfc2231)/[5987](https://datatracker.ietf.org/doc/html/rfc5987) decoding. The extended parameter syntax (`filename*=charset\u0027lang\u0027value`, `name*=...`, and the `filename*0`/`filename*1` continuation form) is decoded and surfaced under the bare `filename`/`name` key, and overrides the plain parameter when both are present. [RFC 7578 \u00a74.2](https://datatracker.ietf.org/doc/html/rfc7578#section-4.2) explicitly forbids the `filename*` form in `multipart/form-data`.\n\nComponents that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for `multipart/form-data` (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.\n\n### Details\n\nGiven both a plain and an extended parameter, the extended value won. For example:\n\n```\nContent-Disposition: form-data; name=\"comment\"; name*=utf-8\u0027\u0027role\n```\n\nAn inspector following RFC 7578 sees the field `comment`, while the returned value was `name=role`. The same applies to filenames:\n\n```\nContent-Disposition: form-data; name=\"upload\"; filename=\"safe.txt\"; filename*=utf-8\u0027\u0027evil.php\n```\n\nThe inspector sees `safe.txt`, while the returned value was `filename=evil.php`. Continuation parameters (`filename*0`, `filename*1`, and so on) were likewise reassembled into a `filename` invisible to a plain `filename=` match, and percent encoded sequences in the extended value were decoded (so `..%2F`, `%00`, and similar appeared in the returned filename).\n\nThis affects the high level `parse_options_header`, `FormParser`, `create_form_parser`, and `parse_form` APIs, and reaches Starlette/FastAPI through `request.form()`, where the smuggled value is exposed as the form field name or [`UploadFile.filename`](https://www.starlette.io/requests/#request-files).\n\n### Impact\n\nThis is an interpretation conflict ([CWE-436](https://cwe.mitre.org/data/definitions/436.html)) with other `multipart/form-data` parsers. An attacker able to submit `multipart/form-data` can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded `..%2F` sequences. Decoded control bytes such as `%00` can likewise cause confusion between an upstream validator and the backend. The `File` class applies `os.path.basename`, so file writing through it is not directly affected.\n\n### Mitigation\n\nUpgrade to `python-multipart` `0.0.30` or later, which ignores RFC 2231/5987 extended parameters (`name*`, `filename*`, and their continuations) so the plain `name`/`filename` parameter remains authoritative. RFC 7578 \u00a74.2 forbids `filename*` for `multipart/form-data`; `name*` and the continuation forms are dropped for the same reason, since they are not valid `multipart/form-data` parameters either.",
  "id": "BREW-gptme-CVE-2026-53537",
  "modified": "2026-09-17T18:12:06Z",
  "published": "2026-08-13T16:54:46Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53537"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Kludex/python-multipart"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/blob/main/vulns/python-multipart/PYSEC-2026-3041.yaml"
    },
    {
      "type": "WEB",
      "url": "https://pypi.org/project/python-multipart"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters",
  "upstream": [
    "GHSA-vffw-93wf-4j4q",
    "CVE-2026-53537",
    "PYSEC-2026-3041"
  ]
}

BREW-HERMES-AGENT-CVE-20… (GHSA-VFFW-93WF-4J4Q)

Vulnerability from osv_homebrew – Published: 2026-08-13 16:56 – Updated: 2026-09-10 19:27 – Source website

Summary

python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters

Details

Summary

parse_options_header parsed Content-Disposition (and Content-Type) headers with email.message.Message, which transparently applies RFC 2231/5987 decoding. The extended parameter syntax (filename*=charset'lang'value, name*=..., and the filename*0/filename*1 continuation form) is decoded and surfaced under the bare filename/name key, and overrides the plain parameter when both are present. RFC 7578 §4.2 explicitly forbids the filename* form in multipart/form-data.

Components that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for multipart/form-data (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.

Details

Given both a plain and an extended parameter, the extended value won. For example:

Content-Disposition: form-data; name="comment"; name*=utf-8''role

An inspector following RFC 7578 sees the field comment, while the returned value was name=role. The same applies to filenames:

Content-Disposition: form-data; name="upload"; filename="safe.txt"; filename*=utf-8''evil.php

The inspector sees safe.txt, while the returned value was filename=evil.php. Continuation parameters (filename*0, filename*1, and so on) were likewise reassembled into a filename invisible to a plain filename= match, and percent encoded sequences in the extended value were decoded (so ..%2F, %00, and similar appeared in the returned filename).

This affects the high level parse_options_header, FormParser, create_form_parser, and parse_form APIs, and reaches Starlette/FastAPI through request.form(), where the smuggled value is exposed as the form field name or UploadFile.filename.

Impact

This is an interpretation conflict (CWE-436) with other multipart/form-data parsers. An attacker able to submit multipart/form-data can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded ..%2F sequences. Decoded control bytes such as %00 can likewise cause confusion between an upstream validator and the backend. The File class applies os.path.basename, so file writing through it is not directly affected.

Mitigation

Upgrade to python-multipart 0.0.30 or later, which ignores RFC 2231/5987 extended parameters (name*, filename*, and their continuations) so the plain name/filename parameter remains authoritative. RFC 7578 §4.2 forbids filename* for multipart/form-data; name* and the continuation forms are dropped for the same reason, since they are not valid multipart/form-data parameters either.

Severity

3.7 (Low)


                    
                      CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

References

URL

Type

	https://github.com/Kludex/python-multipart/securi…	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-53537	ADVISORY
	https://github.com/Kludex/python-multipart	PACKAGE
	https://github.com/advisories/GHSA-vffw-93wf-4j4q	ADVISORY
	https://github.com/pypa/advisory-database/blob/ma…	WEB
	https://pypi.org/project/python-multipart	WEB

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "python-multipart",
        "resource_purl": "pkg:pypi/python-multipart@0.0.32",
        "upstream_fixed_in": "0.0.30"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "hermes-agent",
        "purl": "pkg:brew/hermes-agent"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2026.8.3_1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/python-multipart@0.0.32",
        "name": "python-multipart",
        "resource": "python-multipart",
        "strategy": "registry",
        "subject_version": "0.0.32"
      }
    ]
  },
  "details": "### Summary\n\n`parse_options_header` parsed `Content-Disposition` (and `Content-Type`) headers with [`email.message.Message`](https://docs.python.org/3/library/email.compat32-message.html#email.message.Message), which transparently applies [RFC 2231](https://datatracker.ietf.org/doc/html/rfc2231)/[5987](https://datatracker.ietf.org/doc/html/rfc5987) decoding. The extended parameter syntax (`filename*=charset\u0027lang\u0027value`, `name*=...`, and the `filename*0`/`filename*1` continuation form) is decoded and surfaced under the bare `filename`/`name` key, and overrides the plain parameter when both are present. [RFC 7578 \u00a74.2](https://datatracker.ietf.org/doc/html/rfc7578#section-4.2) explicitly forbids the `filename*` form in `multipart/form-data`.\n\nComponents that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for `multipart/form-data` (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.\n\n### Details\n\nGiven both a plain and an extended parameter, the extended value won. For example:\n\n```\nContent-Disposition: form-data; name=\"comment\"; name*=utf-8\u0027\u0027role\n```\n\nAn inspector following RFC 7578 sees the field `comment`, while the returned value was `name=role`. The same applies to filenames:\n\n```\nContent-Disposition: form-data; name=\"upload\"; filename=\"safe.txt\"; filename*=utf-8\u0027\u0027evil.php\n```\n\nThe inspector sees `safe.txt`, while the returned value was `filename=evil.php`. Continuation parameters (`filename*0`, `filename*1`, and so on) were likewise reassembled into a `filename` invisible to a plain `filename=` match, and percent encoded sequences in the extended value were decoded (so `..%2F`, `%00`, and similar appeared in the returned filename).\n\nThis affects the high level `parse_options_header`, `FormParser`, `create_form_parser`, and `parse_form` APIs, and reaches Starlette/FastAPI through `request.form()`, where the smuggled value is exposed as the form field name or [`UploadFile.filename`](https://www.starlette.io/requests/#request-files).\n\n### Impact\n\nThis is an interpretation conflict ([CWE-436](https://cwe.mitre.org/data/definitions/436.html)) with other `multipart/form-data` parsers. An attacker able to submit `multipart/form-data` can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded `..%2F` sequences. Decoded control bytes such as `%00` can likewise cause confusion between an upstream validator and the backend. The `File` class applies `os.path.basename`, so file writing through it is not directly affected.\n\n### Mitigation\n\nUpgrade to `python-multipart` `0.0.30` or later, which ignores RFC 2231/5987 extended parameters (`name*`, `filename*`, and their continuations) so the plain `name`/`filename` parameter remains authoritative. RFC 7578 \u00a74.2 forbids `filename*` for `multipart/form-data`; `name*` and the continuation forms are dropped for the same reason, since they are not valid `multipart/form-data` parameters either.",
  "id": "BREW-hermes-agent-CVE-2026-53537",
  "modified": "2026-09-10T19:27:17Z",
  "published": "2026-08-13T16:56:26Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53537"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Kludex/python-multipart"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/blob/main/vulns/python-multipart/PYSEC-2026-3041.yaml"
    },
    {
      "type": "WEB",
      "url": "https://pypi.org/project/python-multipart"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters",
  "upstream": [
    "GHSA-vffw-93wf-4j4q",
    "CVE-2026-53537",
    "PYSEC-2026-3041"
  ]
}

BREW-KIMI-CLI-CVE-2026-53537 (GHSA-VFFW-93WF-4J4Q)

Vulnerability from osv_homebrew – Published: 2026-08-13 17:01 – Updated: 2026-09-17 20:03 – Source website

Summary

python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters

Details

Summary

parse_options_header parsed Content-Disposition (and Content-Type) headers with email.message.Message, which transparently applies RFC 2231/5987 decoding. The extended parameter syntax (filename*=charset'lang'value, name*=..., and the filename*0/filename*1 continuation form) is decoded and surfaced under the bare filename/name key, and overrides the plain parameter when both are present. RFC 7578 §4.2 explicitly forbids the filename* form in multipart/form-data.

Components that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for multipart/form-data (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.

Details

Given both a plain and an extended parameter, the extended value won. For example:

Content-Disposition: form-data; name="comment"; name*=utf-8''role

An inspector following RFC 7578 sees the field comment, while the returned value was name=role. The same applies to filenames:

Content-Disposition: form-data; name="upload"; filename="safe.txt"; filename*=utf-8''evil.php

The inspector sees safe.txt, while the returned value was filename=evil.php. Continuation parameters (filename*0, filename*1, and so on) were likewise reassembled into a filename invisible to a plain filename= match, and percent encoded sequences in the extended value were decoded (so ..%2F, %00, and similar appeared in the returned filename).

This affects the high level parse_options_header, FormParser, create_form_parser, and parse_form APIs, and reaches Starlette/FastAPI through request.form(), where the smuggled value is exposed as the form field name or UploadFile.filename.

Impact

This is an interpretation conflict (CWE-436) with other multipart/form-data parsers. An attacker able to submit multipart/form-data can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded ..%2F sequences. Decoded control bytes such as %00 can likewise cause confusion between an upstream validator and the backend. The File class applies os.path.basename, so file writing through it is not directly affected.

Mitigation

Upgrade to python-multipart 0.0.30 or later, which ignores RFC 2231/5987 extended parameters (name*, filename*, and their continuations) so the plain name/filename parameter remains authoritative. RFC 7578 §4.2 forbids filename* for multipart/form-data; name* and the continuation forms are dropped for the same reason, since they are not valid multipart/form-data parameters either.

Severity

3.7 (Low)


                    
                      CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

References

URL

Type

	https://github.com/Kludex/python-multipart/securi…	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-53537	ADVISORY
	https://github.com/Kludex/python-multipart	PACKAGE
	https://github.com/advisories/GHSA-vffw-93wf-4j4q	ADVISORY
	https://github.com/pypa/advisory-database/blob/ma…	WEB
	https://pypi.org/project/python-multipart	WEB

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "python-multipart",
        "resource_purl": "pkg:pypi/python-multipart@0.0.32",
        "upstream_fixed_in": "0.0.30"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "kimi-cli",
        "purl": "pkg:brew/kimi-cli"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.40"
            },
            {
              "fixed": "1.47.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/python-multipart@0.0.32",
        "name": "python-multipart",
        "resource": "python-multipart",
        "strategy": "registry",
        "subject_version": "0.0.32"
      }
    ]
  },
  "details": "### Summary\n\n`parse_options_header` parsed `Content-Disposition` (and `Content-Type`) headers with [`email.message.Message`](https://docs.python.org/3/library/email.compat32-message.html#email.message.Message), which transparently applies [RFC 2231](https://datatracker.ietf.org/doc/html/rfc2231)/[5987](https://datatracker.ietf.org/doc/html/rfc5987) decoding. The extended parameter syntax (`filename*=charset\u0027lang\u0027value`, `name*=...`, and the `filename*0`/`filename*1` continuation form) is decoded and surfaced under the bare `filename`/`name` key, and overrides the plain parameter when both are present. [RFC 7578 \u00a74.2](https://datatracker.ietf.org/doc/html/rfc7578#section-4.2) explicitly forbids the `filename*` form in `multipart/form-data`.\n\nComponents that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for `multipart/form-data` (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.\n\n### Details\n\nGiven both a plain and an extended parameter, the extended value won. For example:\n\n```\nContent-Disposition: form-data; name=\"comment\"; name*=utf-8\u0027\u0027role\n```\n\nAn inspector following RFC 7578 sees the field `comment`, while the returned value was `name=role`. The same applies to filenames:\n\n```\nContent-Disposition: form-data; name=\"upload\"; filename=\"safe.txt\"; filename*=utf-8\u0027\u0027evil.php\n```\n\nThe inspector sees `safe.txt`, while the returned value was `filename=evil.php`. Continuation parameters (`filename*0`, `filename*1`, and so on) were likewise reassembled into a `filename` invisible to a plain `filename=` match, and percent encoded sequences in the extended value were decoded (so `..%2F`, `%00`, and similar appeared in the returned filename).\n\nThis affects the high level `parse_options_header`, `FormParser`, `create_form_parser`, and `parse_form` APIs, and reaches Starlette/FastAPI through `request.form()`, where the smuggled value is exposed as the form field name or [`UploadFile.filename`](https://www.starlette.io/requests/#request-files).\n\n### Impact\n\nThis is an interpretation conflict ([CWE-436](https://cwe.mitre.org/data/definitions/436.html)) with other `multipart/form-data` parsers. An attacker able to submit `multipart/form-data` can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded `..%2F` sequences. Decoded control bytes such as `%00` can likewise cause confusion between an upstream validator and the backend. The `File` class applies `os.path.basename`, so file writing through it is not directly affected.\n\n### Mitigation\n\nUpgrade to `python-multipart` `0.0.30` or later, which ignores RFC 2231/5987 extended parameters (`name*`, `filename*`, and their continuations) so the plain `name`/`filename` parameter remains authoritative. RFC 7578 \u00a74.2 forbids `filename*` for `multipart/form-data`; `name*` and the continuation forms are dropped for the same reason, since they are not valid `multipart/form-data` parameters either.",
  "id": "BREW-kimi-cli-CVE-2026-53537",
  "modified": "2026-09-17T20:03:17Z",
  "published": "2026-08-13T17:01:40Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53537"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Kludex/python-multipart"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/blob/main/vulns/python-multipart/PYSEC-2026-3041.yaml"
    },
    {
      "type": "WEB",
      "url": "https://pypi.org/project/python-multipart"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters",
  "upstream": [
    "GHSA-vffw-93wf-4j4q",
    "CVE-2026-53537",
    "PYSEC-2026-3041"
  ]
}

BREW-MCP-ATLASSIAN-CVE-2… (GHSA-VFFW-93WF-4J4Q)

Vulnerability from osv_homebrew – Published: 2026-08-13 17:13 – Updated: 2026-09-17 19:03 – Source website

Summary

python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters

Details

Summary

parse_options_header parsed Content-Disposition (and Content-Type) headers with email.message.Message, which transparently applies RFC 2231/5987 decoding. The extended parameter syntax (filename*=charset'lang'value, name*=..., and the filename*0/filename*1 continuation form) is decoded and surfaced under the bare filename/name key, and overrides the plain parameter when both are present. RFC 7578 §4.2 explicitly forbids the filename* form in multipart/form-data.

Components that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for multipart/form-data (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.

Details

Given both a plain and an extended parameter, the extended value won. For example:

Content-Disposition: form-data; name="comment"; name*=utf-8''role

An inspector following RFC 7578 sees the field comment, while the returned value was name=role. The same applies to filenames:

Content-Disposition: form-data; name="upload"; filename="safe.txt"; filename*=utf-8''evil.php

The inspector sees safe.txt, while the returned value was filename=evil.php. Continuation parameters (filename*0, filename*1, and so on) were likewise reassembled into a filename invisible to a plain filename= match, and percent encoded sequences in the extended value were decoded (so ..%2F, %00, and similar appeared in the returned filename).

This affects the high level parse_options_header, FormParser, create_form_parser, and parse_form APIs, and reaches Starlette/FastAPI through request.form(), where the smuggled value is exposed as the form field name or UploadFile.filename.

Impact

This is an interpretation conflict (CWE-436) with other multipart/form-data parsers. An attacker able to submit multipart/form-data can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded ..%2F sequences. Decoded control bytes such as %00 can likewise cause confusion between an upstream validator and the backend. The File class applies os.path.basename, so file writing through it is not directly affected.

Mitigation

Upgrade to python-multipart 0.0.30 or later, which ignores RFC 2231/5987 extended parameters (name*, filename*, and their continuations) so the plain name/filename parameter remains authoritative. RFC 7578 §4.2 forbids filename* for multipart/form-data; name* and the continuation forms are dropped for the same reason, since they are not valid multipart/form-data parameters either.

Severity

3.7 (Low)


                    
                      CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

References

URL

Type

	https://github.com/Kludex/python-multipart/securi…	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-53537	ADVISORY
	https://github.com/Kludex/python-multipart	PACKAGE
	https://github.com/advisories/GHSA-vffw-93wf-4j4q	ADVISORY
	https://github.com/pypa/advisory-database/blob/ma…	WEB
	https://pypi.org/project/python-multipart	WEB

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "python-multipart",
        "resource_purl": "pkg:pypi/python-multipart@0.0.32",
        "upstream_fixed_in": "0.0.30"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "mcp-atlassian",
        "purl": "pkg:brew/mcp-atlassian"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.11.9"
            },
            {
              "fixed": "0.21.1_8"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/python-multipart@0.0.32",
        "name": "python-multipart",
        "resource": "python-multipart",
        "strategy": "registry",
        "subject_version": "0.0.32"
      }
    ]
  },
  "details": "### Summary\n\n`parse_options_header` parsed `Content-Disposition` (and `Content-Type`) headers with [`email.message.Message`](https://docs.python.org/3/library/email.compat32-message.html#email.message.Message), which transparently applies [RFC 2231](https://datatracker.ietf.org/doc/html/rfc2231)/[5987](https://datatracker.ietf.org/doc/html/rfc5987) decoding. The extended parameter syntax (`filename*=charset\u0027lang\u0027value`, `name*=...`, and the `filename*0`/`filename*1` continuation form) is decoded and surfaced under the bare `filename`/`name` key, and overrides the plain parameter when both are present. [RFC 7578 \u00a74.2](https://datatracker.ietf.org/doc/html/rfc7578#section-4.2) explicitly forbids the `filename*` form in `multipart/form-data`.\n\nComponents that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for `multipart/form-data` (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.\n\n### Details\n\nGiven both a plain and an extended parameter, the extended value won. For example:\n\n```\nContent-Disposition: form-data; name=\"comment\"; name*=utf-8\u0027\u0027role\n```\n\nAn inspector following RFC 7578 sees the field `comment`, while the returned value was `name=role`. The same applies to filenames:\n\n```\nContent-Disposition: form-data; name=\"upload\"; filename=\"safe.txt\"; filename*=utf-8\u0027\u0027evil.php\n```\n\nThe inspector sees `safe.txt`, while the returned value was `filename=evil.php`. Continuation parameters (`filename*0`, `filename*1`, and so on) were likewise reassembled into a `filename` invisible to a plain `filename=` match, and percent encoded sequences in the extended value were decoded (so `..%2F`, `%00`, and similar appeared in the returned filename).\n\nThis affects the high level `parse_options_header`, `FormParser`, `create_form_parser`, and `parse_form` APIs, and reaches Starlette/FastAPI through `request.form()`, where the smuggled value is exposed as the form field name or [`UploadFile.filename`](https://www.starlette.io/requests/#request-files).\n\n### Impact\n\nThis is an interpretation conflict ([CWE-436](https://cwe.mitre.org/data/definitions/436.html)) with other `multipart/form-data` parsers. An attacker able to submit `multipart/form-data` can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded `..%2F` sequences. Decoded control bytes such as `%00` can likewise cause confusion between an upstream validator and the backend. The `File` class applies `os.path.basename`, so file writing through it is not directly affected.\n\n### Mitigation\n\nUpgrade to `python-multipart` `0.0.30` or later, which ignores RFC 2231/5987 extended parameters (`name*`, `filename*`, and their continuations) so the plain `name`/`filename` parameter remains authoritative. RFC 7578 \u00a74.2 forbids `filename*` for `multipart/form-data`; `name*` and the continuation forms are dropped for the same reason, since they are not valid `multipart/form-data` parameters either.",
  "id": "BREW-mcp-atlassian-CVE-2026-53537",
  "modified": "2026-09-17T19:03:07Z",
  "published": "2026-08-13T17:13:13Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53537"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Kludex/python-multipart"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/blob/main/vulns/python-multipart/PYSEC-2026-3041.yaml"
    },
    {
      "type": "WEB",
      "url": "https://pypi.org/project/python-multipart"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters",
  "upstream": [
    "GHSA-vffw-93wf-4j4q",
    "CVE-2026-53537",
    "PYSEC-2026-3041"
  ]
}

BREW-MCP-GOOGLE-SHEETS-C… (GHSA-VFFW-93WF-4J4Q)

Vulnerability from osv_homebrew – Published: 2026-08-13 17:13 – Updated: 2026-09-17 18:01 – Source website

Summary

python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters

Details

Summary

parse_options_header parsed Content-Disposition (and Content-Type) headers with email.message.Message, which transparently applies RFC 2231/5987 decoding. The extended parameter syntax (filename*=charset'lang'value, name*=..., and the filename*0/filename*1 continuation form) is decoded and surfaced under the bare filename/name key, and overrides the plain parameter when both are present. RFC 7578 §4.2 explicitly forbids the filename* form in multipart/form-data.

Components that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for multipart/form-data (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.

Details

Given both a plain and an extended parameter, the extended value won. For example:

Content-Disposition: form-data; name="comment"; name*=utf-8''role

An inspector following RFC 7578 sees the field comment, while the returned value was name=role. The same applies to filenames:

Content-Disposition: form-data; name="upload"; filename="safe.txt"; filename*=utf-8''evil.php

The inspector sees safe.txt, while the returned value was filename=evil.php. Continuation parameters (filename*0, filename*1, and so on) were likewise reassembled into a filename invisible to a plain filename= match, and percent encoded sequences in the extended value were decoded (so ..%2F, %00, and similar appeared in the returned filename).

This affects the high level parse_options_header, FormParser, create_form_parser, and parse_form APIs, and reaches Starlette/FastAPI through request.form(), where the smuggled value is exposed as the form field name or UploadFile.filename.

Impact

This is an interpretation conflict (CWE-436) with other multipart/form-data parsers. An attacker able to submit multipart/form-data can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded ..%2F sequences. Decoded control bytes such as %00 can likewise cause confusion between an upstream validator and the backend. The File class applies os.path.basename, so file writing through it is not directly affected.

Mitigation

Upgrade to python-multipart 0.0.30 or later, which ignores RFC 2231/5987 extended parameters (name*, filename*, and their continuations) so the plain name/filename parameter remains authoritative. RFC 7578 §4.2 forbids filename* for multipart/form-data; name* and the continuation forms are dropped for the same reason, since they are not valid multipart/form-data parameters either.

Severity

3.7 (Low)


                    
                      CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

References

URL

Type

	https://github.com/Kludex/python-multipart/securi…	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-53537	ADVISORY
	https://github.com/Kludex/python-multipart	PACKAGE
	https://github.com/advisories/GHSA-vffw-93wf-4j4q	ADVISORY
	https://github.com/pypa/advisory-database/blob/ma…	WEB
	https://pypi.org/project/python-multipart	WEB

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "python-multipart",
        "resource_purl": "pkg:pypi/python-multipart@0.0.32",
        "upstream_fixed_in": "0.0.30"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "mcp-google-sheets",
        "purl": "pkg:brew/mcp-google-sheets"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.5.1"
            },
            {
              "fixed": "0.6.3_2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/python-multipart@0.0.32",
        "name": "python-multipart",
        "resource": "python-multipart",
        "strategy": "registry",
        "subject_version": "0.0.32"
      }
    ]
  },
  "details": "### Summary\n\n`parse_options_header` parsed `Content-Disposition` (and `Content-Type`) headers with [`email.message.Message`](https://docs.python.org/3/library/email.compat32-message.html#email.message.Message), which transparently applies [RFC 2231](https://datatracker.ietf.org/doc/html/rfc2231)/[5987](https://datatracker.ietf.org/doc/html/rfc5987) decoding. The extended parameter syntax (`filename*=charset\u0027lang\u0027value`, `name*=...`, and the `filename*0`/`filename*1` continuation form) is decoded and surfaced under the bare `filename`/`name` key, and overrides the plain parameter when both are present. [RFC 7578 \u00a74.2](https://datatracker.ietf.org/doc/html/rfc7578#section-4.2) explicitly forbids the `filename*` form in `multipart/form-data`.\n\nComponents that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for `multipart/form-data` (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend.\n\n### Details\n\nGiven both a plain and an extended parameter, the extended value won. For example:\n\n```\nContent-Disposition: form-data; name=\"comment\"; name*=utf-8\u0027\u0027role\n```\n\nAn inspector following RFC 7578 sees the field `comment`, while the returned value was `name=role`. The same applies to filenames:\n\n```\nContent-Disposition: form-data; name=\"upload\"; filename=\"safe.txt\"; filename*=utf-8\u0027\u0027evil.php\n```\n\nThe inspector sees `safe.txt`, while the returned value was `filename=evil.php`. Continuation parameters (`filename*0`, `filename*1`, and so on) were likewise reassembled into a `filename` invisible to a plain `filename=` match, and percent encoded sequences in the extended value were decoded (so `..%2F`, `%00`, and similar appeared in the returned filename).\n\nThis affects the high level `parse_options_header`, `FormParser`, `create_form_parser`, and `parse_form` APIs, and reaches Starlette/FastAPI through `request.form()`, where the smuggled value is exposed as the form field name or [`UploadFile.filename`](https://www.starlette.io/requests/#request-files).\n\n### Impact\n\nThis is an interpretation conflict ([CWE-436](https://cwe.mitre.org/data/definitions/436.html)) with other `multipart/form-data` parsers. An attacker able to submit `multipart/form-data` can present a different field name or filename to an upstream body inspecting component than the one delivered to the application. Concrete consequences depend on how the application uses these values, and may include bypassing a field name or filename based access/upload control, or, for an application that builds filesystem paths from the parsed filename without sanitization, path traversal via decoded `..%2F` sequences. Decoded control bytes such as `%00` can likewise cause confusion between an upstream validator and the backend. The `File` class applies `os.path.basename`, so file writing through it is not directly affected.\n\n### Mitigation\n\nUpgrade to `python-multipart` `0.0.30` or later, which ignores RFC 2231/5987 extended parameters (`name*`, `filename*`, and their continuations) so the plain `name`/`filename` parameter remains authoritative. RFC 7578 \u00a74.2 forbids `filename*` for `multipart/form-data`; `name*` and the continuation forms are dropped for the same reason, since they are not valid `multipart/form-data` parameters either.",
  "id": "BREW-mcp-google-sheets-CVE-2026-53537",
  "modified": "2026-09-17T18:01:45Z",
  "published": "2026-08-13T17:13:13Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53537"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Kludex/python-multipart"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-vffw-93wf-4j4q"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/blob/main/vulns/python-multipart/PYSEC-2026-3041.yaml"
    },
    {
      "type": "WEB",
      "url": "https://pypi.org/project/python-multipart"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "python-multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters",
  "upstream": [
    "GHSA-vffw-93wf-4j4q",
    "CVE-2026-53537",
    "PYSEC-2026-3041"
  ]
}

CVE-2026-53537 (GCVE-0-2026-53537)

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Related by attack behaviour

Action not permitted

CVE-2026-53537 (GCVE-0-2026-53537)

BREW-CYCODE-CVE-2026-53537 (GHSA-VFFW-93WF-4J4Q)

Summary

Details

Impact

Mitigation

BREW-DATASETTE-CVE-2026-53537 (GHSA-VFFW-93WF-4J4Q)

Summary

Details

Impact

Mitigation

BREW-DSTACK-CVE-2026-53537 (GHSA-VFFW-93WF-4J4Q)

Summary

Details

Impact

Mitigation

BREW-FASTAPI-CVE-2026-53537 (GHSA-VFFW-93WF-4J4Q)

Summary

Details

Impact

Mitigation

BREW-FASTMCP-CVE-2026-53537 (GHSA-VFFW-93WF-4J4Q)

Summary

Details

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Mitigation

BREW-GPTME-CVE-2026-53537 (GHSA-VFFW-93WF-4J4Q)

Summary

Details

Impact

Mitigation

BREW-HERMES-AGENT-CVE-20… (GHSA-VFFW-93WF-4J4Q)

Summary

Details

Impact

Mitigation

BREW-KIMI-CLI-CVE-2026-53537 (GHSA-VFFW-93WF-4J4Q)

Summary

Details

Impact

Mitigation

BREW-MCP-ATLASSIAN-CVE-2… (GHSA-VFFW-93WF-4J4Q)

Summary

Details

Impact

Mitigation

BREW-MCP-GOOGLE-SHEETS-C… (GHSA-VFFW-93WF-4J4Q)

Summary

Details

Impact

Mitigation

Tags

Sightings

Nomenclature

Related by attack behaviour