Vulnerability-Lookup

CVE-2026-48818 (GCVE-0-2026-48818)

Vulnerability from cvelistv5 – Published: 2026-06-17 17:50 – Updated: 2026-06-17 19:31

Title

Starlette: SSRF and NTLM credential theft via UNC paths in StaticFiles on Windows

Summary

Starlette is a lightweight ASGI framework/toolkit. In versions 1.0.1 and earlier, StaticFiles on Windows is vulnerable to SSRF. An UNC path such as \\attacker.com\share can cause os.path.realpath to initiate an outbound SMB connection before the path is rejected, exposing the service account’s NTLMv2 credentials for offline cracking or relay even though the HTTP response is only a 404. The issue affects default follow_symlink=False deployments, including frameworks built on Starlette such as FastAPI; POSIX systems and follow_symlink=True are unaffected. The issue is fixed in 1.1.0.

Severity

7.5 (High)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-918 - Server-Side Request Forgery (SSRF)

Assigner

GitHub_M

References

4 references

URL	Tags
https://github.com/Kludex/starlette/security/advi…	x_refsource_CONFIRM
https://github.com/Kludex/starlette/pull/3287	x_refsource_MISC
https://github.com/Kludex/starlette/commit/fd5316…	x_refsource_MISC
https://github.com/Kludex/starlette/releases/tag/1.1.0	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
Kludex	starlette	Affected: < 1.1.0

Show details on NVD website

JSON

To clipboard

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                "id": "CVE-2026-48818",
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FKIE_CVE-2026-48818

Vulnerability from fkie_nvd - Published: 2026-06-17 19:18 - Updated: 2026-06-17 20:17

Severity

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/Kludex/starlette/commit/fd53168a7767b6b55ba5af787fd88f49e33cabc5
	security-advisories@github.com	https://github.com/Kludex/starlette/pull/3287
	security-advisories@github.com	https://github.com/Kludex/starlette/releases/tag/1.1.0
	security-advisories@github.com	https://github.com/Kludex/starlette/security/advisories/GHSA-wqp7-x3pw-xc5r

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "starlette",
          "vendor": "Kludex",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.1.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Starlette is a lightweight ASGI framework/toolkit. In versions 1.0.1 and earlier, StaticFiles on Windows is vulnerable to SSRF. An UNC path such as \\\\attacker.com\\share can cause os.path.realpath to initiate an outbound SMB connection before the path is rejected, exposing the service account\u2019s NTLMv2 credentials for offline cracking or relay even though the HTTP response is only a 404. The issue affects default follow_symlink=False deployments, including frameworks built on Starlette such as FastAPI; POSIX systems and follow_symlink=True are unaffected. The issue is fixed in 1.1.0."
    }
  ],
  "id": "CVE-2026-48818",
  "lastModified": "2026-06-17T20:17:22.583",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
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          "options": [
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              "automatable": "yes"
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              "technicalImpact": "partial"
            }
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          "role": "CISA Coordinator",
          "timestamp": "2026-06-17T19:31:32.312592Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-06-17T19:18:09.807",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Kludex/starlette/commit/fd53168a7767b6b55ba5af787fd88f49e33cabc5"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Kludex/starlette/pull/3287"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Kludex/starlette/releases/tag/1.1.0"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/Kludex/starlette/security/advisories/GHSA-wqp7-x3pw-xc5r"
    }
  ],
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  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
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      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-WQP7-X3PW-XC5R

Vulnerability from github – Published: 2026-06-15 20:16 – Updated: 2026-06-15 20:16

Summary

Starlette: SSRF and NTLM credential theft via UNC paths in StaticFiles on Windows

Details

Summary

When serving static files on Windows, StaticFiles resolves the requested path with os.path.realpath. If a UNC path (such as \\attacker.com\share) reaches the resolver, realpath causes the process to open a connection to the remote host over SMB (port 445). This is a server-side request forgery (SSRF) that leaks the service account's NTLMv2 credentials to the attacker-controlled host, which can then be cracked offline or relayed to other hosts.

Details

StaticFiles.lookup_path() joins the requested path onto the served directory and calls os.path.realpath on the result before checking containment with os.path.commonpath. On Windows, a UNC path is absolute, so os.path.join discards the served directory and realpath resolves the bare UNC path, triggering the outbound SMB connection and NTLM authentication before the containment check rejects the path. The HTTP response is a benign 404, but the credential disclosure has already happened. POSIX systems are not affected.

This only affects the default configuration (follow_symlink=False), which uses os.path.realpath. The follow_symlink=True branch uses os.path.abspath, which performs no I/O.

Impact

Applications running on Windows that serve files with StaticFiles (directly, or via a framework built on Starlette such as FastAPI) in the default configuration are affected. StaticFiles is typically unauthenticated, so any client can trigger the SMB connection and leak the service account's NTLMv2 hash. A secondary impact is discovering internal hosts reachable over SMB by timing responses for valid versus invalid addresses.

Mitigation

Applications not running on Windows are not affected. On Windows, serving static files through a dedicated web server (such as nginx or IIS) instead of StaticFiles avoids the issue. Blocking outbound SMB (port 445) from the application host prevents the credential disclosure even if a UNC path is resolved.

Severity

7.5 (High)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "starlette"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.1.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-48818"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-918"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-15T20:16:30Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Summary\n\nWhen serving static files on Windows, `StaticFiles` resolves the requested path with [`os.path.realpath`](https://docs.python.org/3/library/os.path.html#os.path.realpath). If a UNC path (such as `\\\\attacker.com\\share`) reaches the resolver, `realpath` causes the process to open a connection to the remote host over SMB (port 445). This is a server-side request forgery (SSRF) that leaks the service account\u0027s NTLMv2 credentials to the attacker-controlled host, which can then be cracked offline or relayed to other hosts.\n\n### Details\n\n`StaticFiles.lookup_path()` joins the requested path onto the served directory and calls [`os.path.realpath`](https://docs.python.org/3/library/os.path.html#os.path.realpath) on the result before checking containment with [`os.path.commonpath`](https://docs.python.org/3/library/os.path.html#os.path.commonpath). On Windows, a UNC path is absolute, so [`os.path.join`](https://docs.python.org/3/library/os.path.html#os.path.join) discards the served directory and `realpath` resolves the bare UNC path, triggering the outbound SMB connection and NTLM authentication before the containment check rejects the path. The HTTP response is a benign 404, but the credential disclosure has already happened. POSIX systems are not affected.\n\nThis only affects the default configuration (`follow_symlink=False`), which uses [`os.path.realpath`](https://docs.python.org/3/library/os.path.html#os.path.realpath). The `follow_symlink=True` branch uses [`os.path.abspath`](https://docs.python.org/3/library/os.path.html#os.path.abspath), which performs no I/O.\n\n### Impact\n\nApplications running on Windows that serve files with `StaticFiles` (directly, or via a framework built on Starlette such as FastAPI) in the default configuration are affected. `StaticFiles` is typically unauthenticated, so any client can trigger the SMB connection and leak the service account\u0027s NTLMv2 hash. A secondary impact is discovering internal hosts reachable over SMB by timing responses for valid versus invalid addresses.\n\n### Mitigation\n\nApplications not running on Windows are not affected. On Windows, serving static files through a dedicated web server (such as nginx or IIS) instead of `StaticFiles` avoids the issue. Blocking outbound SMB (port 445) from the application host prevents the credential disclosure even if a UNC path is resolved.",
  "id": "GHSA-wqp7-x3pw-xc5r",
  "modified": "2026-06-15T20:16:30Z",
  "published": "2026-06-15T20:16:30Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Kludex/starlette/security/advisories/GHSA-wqp7-x3pw-xc5r"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Kludex/starlette"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Starlette: SSRF and NTLM credential theft via UNC paths in StaticFiles on Windows"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-48818 (GCVE-0-2026-48818)

FKIE_CVE-2026-48818

GHSA-WQP7-X3PW-XC5R

Summary

Details

Impact

Mitigation

Tags

Sightings

Nomenclature