Vulnerability-Lookup

CVE-2026-47261 (GCVE-0-2026-47261)

Vulnerability from cvelistv5 – Published: 2026-06-15 19:47 – Updated: 2026-06-16 12:46

Title

Wasmtime: WASI path_open(TRUNCATE) bypasses `FilePerms::WRITE` host restriction

Summary

Wasmtime is a runtime for WebAssembly. In versions prior to 24.0.9, 36.0.10, and 44.0.2, when a filesystem preopen is given DirPerms::all() and FilePerms::READ without FilePerms::WRITE, this access control mechanism can be bypassed via the wasip2 descriptor.open-at or wasip1 path_open interfaces by opening a file with only the OpenFlags::TRUNCATE oflag. The root cause is that the clause handling OpenFlags::TRUNCATE in crates/wasi/src/filesystem.rs (Dir::open_at, lines 967–969) did not set open_mode |= OpenMode::WRITE;, which is later used for the access control check against FilePerms to determine whether opening the file is permitted; the single-line fix adds that missing assignment, after which the affected calls correctly fail with error-code.not-permitted and ERRNO_PERM respectively. Only wasmtime-wasi embeddings that combine DirPerms::MUTATE with FilePerms::READ are affected by this bug. In particular, the Wasmtime project's wasmtime-cli's use of wasmtime-wasi is not affected, because it always sets FilePerms::all() for all preopens. This issue has been fixed in versions 24.0.9, 36.0.10 and44.0.2.

Severity

7.5 (High)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-284 - Improper Access Control

Assigner

GitHub_M

References

5 references

URL	Tags
https://github.com/bytecodealliance/wasmtime/secu…	x_refsource_CONFIRM
https://github.com/bytecodealliance/wasmtime/rele…	x_refsource_MISC
https://github.com/bytecodealliance/wasmtime/rele…	x_refsource_MISC
https://github.com/bytecodealliance/wasmtime/rele…	x_refsource_MISC
https://github.com/bytecodealliance/wasmtime/rele…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
bytecodealliance	wasmtime	Affected: >= 37.0.0, < 44.0.2 Affected: >= 25.0.0, < 36.0.10 Affected: < 24.0.9

Show details on NVD website

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FKIE_CVE-2026-47261

Vulnerability from fkie_nvd - Published: 2026-06-15 21:17 - Updated: 2026-06-17 16:42

Severity

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

Summary

References

URL	Tags
security-advisories@github.com	https://github.com/bytecodealliance/wasmtime/releases/tag/v24.0.9	Release Notes
security-advisories@github.com	https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.10	Release Notes
security-advisories@github.com	https://github.com/bytecodealliance/wasmtime/releases/tag/v44.0.2	Release Notes
security-advisories@github.com	https://github.com/bytecodealliance/wasmtime/releases/tag/v45.0.0	Release Notes
security-advisories@github.com	https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-2r75-cxrj-cmph	Mitigation, Vendor Advisory

Impacted products

Vendor	Product	Version
bytecodealliance	wasmtime	*
bytecodealliance	wasmtime	*
bytecodealliance	wasmtime	*

JSON

To clipboard

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          "product": "wasmtime",
          "vendor": "bytecodealliance",
          "versions": [
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              "version": "\u003e= 37.0.0, \u003c 44.0.2"
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              "version": "\u003e= 25.0.0, \u003c 36.0.10"
            },
            {
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      "source": "security-advisories@github.com"
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  ],
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              "versionEndExcluding": "24.0.9",
              "vulnerable": true
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              "versionEndExcluding": "44.0.2",
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  ],
  "id": "CVE-2026-47261",
  "lastModified": "2026-06-17T16:42:08.350",
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      "source": "nvd@nist.gov",
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}

GHSA-2R75-CXRJ-CMPH

Vulnerability from github – Published: 2026-06-05 15:47 – Updated: 2026-06-05 15:47

Summary

wasmtime-wasi: WASI path_open(TRUNCATE) bypasses `FilePerms::WRITE` host restriction

Details

Summary

In wasmtime-wasi, when a filesystem preopen is given DirPerms::all() and FilePerms::READ without FilePerms::WRITE, this wasmtime-wasi enforced access control mechanism can be bypassed by using the wasip2 descriptor.open-at or wasip1 path_open interfaces by opening a file with OpenFlags::TRUNCATE oflag only, for example:

dir_descriptor.open_at(
   PathFlags::empty(),
   FILENAME,
   OpenFlags::TRUNCATE,
   DescriptorFlags::READ,
)

wasip1::path_open(
    dir_fd,
    0,
    FILENAME,
    wasip1::OFLAGS_TRUNC,
    wasip1::RIGHTS_FD_READ,
    0,
    0
)

The root cause is that the clause that considered OpenFlags::TRUNCATE did not set open_mode |= OpenMode::WRITE;, used later in that function for the access control check against FilePerms for whether opening that file is permitted. With the bug corrected, these calls to open-at and path_open fail with error-code.not-permitted and ERRNO_PERM respectively.

The bug in crates/wasi/src/filesystem.rs, Dir::open_at, lines 967–969:

if oflags.contains(OpenFlags::TRUNCATE) {
    opts.truncate(true).write(true);
}

and the single line fix is:

if oflags.contains(OpenFlags::TRUNCATE) {
    opts.truncate(true).write(true);
    open_mode |= OpenMode::WRITE;
}

Only wasmtime-wasi embeddings that use a combination of DirPerms::MUTATE with FilePerms::READ are affected by this bug, e.g. those that use in the WasiCtxBuilder:

builder.preopened_dir("readonly", "readonly", DirPerms::READ | DirPerms::MUTATE, FilePerms::READ);

In particular, the Wasmtime project's wasmtime-cli's use of wasmtime-wasi is not affected, because it always sets FilePerms::all() for all preopens.

Severity

7.5 (High)


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

Show details on source website

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{
  "affected": [
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "wasmtime-wasi"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "37.0.0"
            },
            {
              "fixed": "44.0.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "wasmtime-wasi"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "25.0.0"
            },
            {
              "fixed": "36.0.10"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "wasmtime-wasi"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "24.0.9"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-47261"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-284"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-05T15:47:02Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "## Summary\n\nIn `wasmtime-wasi`, when a filesystem preopen is given `DirPerms::all()` and `FilePerms::READ` without `FilePerms::WRITE`,  this wasmtime-wasi enforced access control mechanism can be bypassed by using the wasip2 `descriptor.open-at` or wasip1 `path_open` interfaces by opening a file with `OpenFlags::TRUNCATE` oflag only, for example:\n\n```rust\ndir_descriptor.open_at(\n   PathFlags::empty(),\n   FILENAME,\n   OpenFlags::TRUNCATE,\n   DescriptorFlags::READ,\n)\n```\n\n```rust\nwasip1::path_open(\n    dir_fd,\n    0,\n    FILENAME,\n    wasip1::OFLAGS_TRUNC,\n    wasip1::RIGHTS_FD_READ,\n    0,\n    0\n)\n```\n\nThe root cause is that the clause that considered `OpenFlags::TRUNCATE` did not set `open_mode |= OpenMode::WRITE;`, used later in that function for the access control check against `FilePerms` for whether opening that file is permitted. With the bug corrected, these calls to `open-at` and `path_open` fail with `error-code.not-permitted` and `ERRNO_PERM` respectively.\n\nThe bug in `crates/wasi/src/filesystem.rs`, `Dir::open_at`, lines 967\u2013969:\n\n```rust\nif oflags.contains(OpenFlags::TRUNCATE) {\n    opts.truncate(true).write(true);\n}\n```\nand the single line fix is:\n```rust\nif oflags.contains(OpenFlags::TRUNCATE) {\n    opts.truncate(true).write(true);\n    open_mode |= OpenMode::WRITE;\n}\n```\n\nOnly wasmtime-wasi embeddings that use a combination of DirPerms::MUTATE with FilePerms::READ are affected by this bug, e.g. those that use in the `WasiCtxBuilder`:\n```rust\nbuilder.preopened_dir(\"readonly\", \"readonly\", DirPerms::READ | DirPerms::MUTATE, FilePerms::READ);\n```\n\nIn particular, the Wasmtime project\u0027s `wasmtime-cli`\u0027s use of wasmtime-wasi is not affected, because it always sets `FilePerms::all()` for all preopens.",
  "id": "GHSA-2r75-cxrj-cmph",
  "modified": "2026-06-05T15:47:02Z",
  "published": "2026-06-05T15:47:02Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-2r75-cxrj-cmph"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/bytecodealliance/wasmtime"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/releases/tag/v24.0.9"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.10"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/releases/tag/v44.0.2"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/releases/tag/v45.0.0"
    },
    {
      "type": "WEB",
      "url": "https://rustsec.org/advisories/RUSTSEC-2026-0149.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "wasmtime-wasi: WASI path_open(TRUNCATE) bypasses `FilePerms::WRITE` host restriction"
}

rustsec-2026-0149

Vulnerability from osv_rustsec

Published

2026-05-21 12:00

Modified

2026-05-22 10:02

Summary

WASI path_open(TRUNCATE) bypasses `FilePerms::WRITE` host restriction

Details

This is an entry in the RustSec database for the Wasmtime security advisory located at https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-2r75-cxrj-cmph For more information see the GitHub-hosted security advisory.

Severity

7.5 (High)


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

References

URL

Type

	https://crates.io/crates/wasmtime-wasi	PACKAGE
	https://rustsec.org/advisories/RUSTSEC-2026-0149.html	ADVISORY
	https://github.com/bytecodealliance/wasmtime/secu…	ADVISORY

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "categories": [],
        "cvss": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
        "informational": null
      },
      "ecosystem_specific": {
        "affected_functions": null,
        "affects": {
          "arch": [],
          "functions": [],
          "os": []
        }
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "wasmtime-wasi",
        "purl": "pkg:cargo/wasmtime-wasi"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.0.0-0"
            },
            {
              "fixed": "24.0.9"
            },
            {
              "introduced": "25.0.0"
            },
            {
              "fixed": "36.0.10"
            },
            {
              "introduced": "37.0.0"
            },
            {
              "fixed": "44.0.2"
            },
            {
              "introduced": "45.0.0"
            },
            {
              "fixed": "45.0.0"
            }
          ],
          "type": "SEMVER"
        }
      ],
      "versions": []
    }
  ],
  "aliases": [
    "CVE-2026-47261",
    "GHSA-2r75-cxrj-cmph"
  ],
  "database_specific": {
    "license": "CC0-1.0"
  },
  "details": "This is an entry in the RustSec database for the Wasmtime security advisory\nlocated at\nhttps://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-2r75-cxrj-cmph\nFor more information see the GitHub-hosted security advisory.",
  "id": "RUSTSEC-2026-0149",
  "modified": "2026-05-22T10:02:28Z",
  "published": "2026-05-21T12:00:00Z",
  "references": [
    {
      "type": "PACKAGE",
      "url": "https://crates.io/crates/wasmtime-wasi"
    },
    {
      "type": "ADVISORY",
      "url": "https://rustsec.org/advisories/RUSTSEC-2026-0149.html"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-2r75-cxrj-cmph"
    }
  ],
  "related": [],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "WASI path_open(TRUNCATE) bypasses `FilePerms::WRITE` host restriction"
}

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-2026-47261 (GCVE-0-2026-47261)

FKIE_CVE-2026-47261

GHSA-2R75-CXRJ-CMPH

Summary

rustsec-2026-0149

Vulnerability from osv_rustsec

Tags

Sightings

Nomenclature