GHSA-243V-98VX-264H

Vulnerability from github – Published: 2026-02-24 21:08 – Updated: 2026-02-24 21:08
VLAI?
Summary
Wasmtime can panic when adding excessive fields to a `wasi:http/types.fields` instance
Details

Impact

Wasmtime's implementation of the wasi:http/types.fields resource is susceptible to panics when too many fields are added to the set of headers. Wasmtime's implementation in the wasmtime-wasi-http crate is backed by a data structure which panics when it reaches excessive capacity and this condition was not handled gracefully in Wasmtime. Panicking in a WASI implementation is a Denial of Service vector for embedders and is treated as a security vulnerability in Wasmtime.

Patches

Wasmtime 24.0.6, 36.0.6, 40.0.4, 41.0.4, and 42.0.0 patch this vulnerability and return a trap to the guest instead of panicking.

Workarounds

There are no known workarounds at this time, embedders are encouraged to update to a patched version of Wasmtime.

Resources

Severity ?
6.9 (Medium)
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
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{
  "affected": [
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "wasmtime"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "24.0.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "wasmtime"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "25.0.0"
            },
            {
              "fixed": "36.0.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "wasmtime"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "37.0.0"
            },
            {
              "fixed": "40.0.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "wasmtime"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "41.0.0"
            },
            {
              "fixed": "41.0.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-27572"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-24T21:08:06Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Impact\n\nWasmtime\u0027s implementation of the `wasi:http/types.fields` resource is susceptible to panics when too many fields are added to the set of headers. Wasmtime\u0027s implementation in the `wasmtime-wasi-http` crate is backed by a data structure which panics when it reaches excessive capacity and this condition was not handled gracefully in Wasmtime. Panicking in a WASI implementation is a Denial of Service vector for embedders and is treated as a security vulnerability in Wasmtime.\n\n### Patches\n\nWasmtime 24.0.6, 36.0.6, 40.0.4, 41.0.4, and 42.0.0 patch this vulnerability and return a trap to the guest instead of panicking.\n\n### Workarounds\n\nThere are no known workarounds at this time, embedders are encouraged to update to a patched version of Wasmtime.\n\n### Resources\n\n* [Limitations of `http::HeaderMap`](https://docs.rs/http/1.4.0/http/header/#limitations)",
  "id": "GHSA-243v-98vx-264h",
  "modified": "2026-02-24T21:08:06Z",
  "published": "2026-02-24T21:08:06Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-243v-98vx-264h"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/commit/301dc7162cca51def19131019af1187f45901c0a"
    },
    {
      "type": "WEB",
      "url": "https://docs.rs/http/1.4.0/http/header/#limitations"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/bytecodealliance/wasmtime"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/releases/tag/v24.0.6"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.6"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/releases/tag/v40.0.4"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bytecodealliance/wasmtime/releases/tag/v41.0.4"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Wasmtime can panic when adding excessive fields to a `wasi:http/types.fields` instance"
}


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