CVE-2026-27572: Wasmtime Http/types.fields` Instance Vulnerability

MODERATE
Advisory Identifier: GHSA-243v-98vx-264h
Share
CWE-770
Published
Advisory Summary

CVE-2026-27572 is a MODERATE http/types.fields` instance vulnerability (CWE-770: Allocation of Resources Without Limits or Throttling) affecting Wasmtime libraries in the crates.io ecosystem. The issue involves http/types.fields` instance. Remediation is available by upgrading affected packages to version 24.0.6, 36.0.6, 40.0.4.

CVE-2026-27572 at a Glance

CVE Identifier CVE-2026-27572
GHSA Identifier GHSA-243v-98vx-264h
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-770: Allocation of Resources Without Limits or Throttling
Affected Product Wasmtime
Package Ecosystem crates.io
Published Date
Last Updated

How to Fix CVE-2026-27572

To remediate this vulnerability, upgrade all affected Wasmtime dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

wasmtime fixed: 24.0.6 
Upgrade wasmtime to 24.0.6
wasmtime fixed: 36.0.6 
Upgrade wasmtime to 36.0.6
wasmtime fixed: 40.0.4 
Upgrade wasmtime to 40.0.4
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for wasmtime

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-27572, inspect your project dependencies for Wasmtime:

inspect dependencies for wasmtime

Analyze the terminal output to locate any version of Wasmtime in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 24.0.6), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-770: Allocation of Resources Without Limits or Throttling, where the product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. In Wasmtime, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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 * [Limitations of `http::HeaderMap`](https://docs.rs/http/1.4.0/http/header/#limitations)

CVE-2026-27572 Affected Wasmtime Versions

3 component(s)
Fixed Versions:
24.0.636.0.640.0.4
Product / Package Ecosystem Affected Versions Fixed Version
wasmtime
 crates.io
< 24.0.6
24.0.6
wasmtime
 crates.io
≥ 25.0.0
< 36.0.6
36.0.6
wasmtime
 crates.io
≥ 37.0.0
< 40.0.4
40.0.4

References

GitHub Advisory / Wiki ADVISORY
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-243v-98vx-264h
NVD — CVE-2026-27572 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-27572
Security Fix Commit FIX COMMIT
https://github.com/bytecodealliance/wasmtime/commit/301dc7162cca51def19131019af1187f45901c0a
docs.rs/http/1.4.0/http/hea... WEB
https://docs.rs/http/1.4.0/http/header/#limitations
Wasmtime Source Repository REPOSITORY
https://github.com/bytecodealliance/wasmtime
Wasmtime Release RELEASE
https://github.com/bytecodealliance/wasmtime/releases/tag/v24.0.6
Wasmtime Release RELEASE
https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.6
Wasmtime Release RELEASE
https://github.com/bytecodealliance/wasmtime/releases/tag/v40.0.4
Wasmtime Release RELEASE
https://github.com/bytecodealliance/wasmtime/releases/tag/v41.0.4
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2026-0021.html

Frequently Asked Questions

What is CVE-2026-27572?
CVE-2026-27572 is a security vulnerability in Wasmtime involving http/types.fields` instance under CWE-770: Allocation of Resources Without Limits or Throttling.
Which Wasmtime versions are affected?
Affected versions include releases prior to 24.0.6, 36.0.6, 40.0.4 across affected packages: wasmtime.
What version fixes CVE-2026-27572?
Upgrading to 24.0.6, 36.0.6, 40.0.4 (or the latest patched release for your respective branch) resolves the vulnerability.
Is wasmtime affected?
Yes, wasmtime is affected in releases prior to 24.0.6, 36.0.6, 40.0.4. Upgrade your dependency to 24.0.6, 36.0.6, 40.0.4 or later.
What CWE is associated with CVE-2026-27572?
CVE-2026-27572 is classified under CWE-770: Allocation of Resources Without Limits or Throttling (The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.).
How can I check crates.io dependencies for CVE-2026-27572?
Run the dependency tree command: 'inspect dependencies for wasmtime'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-243v-98vx-264h",
  "modified" : "2026-02-27T20:25:44Z",
  "published" : "2026-02-24T21:08:06Z",
  "aliases" : [ "CVE-2026-27572" ],
  "summary" : "Wasmtime can panic when adding excessive fields to a `wasi:http/types.fields` instance",
  "details" : "### Impact\n\nWasmtime'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.\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)",
  "severity" : [ {
    "type" : "CVSS_V4",
    "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "wasmtime"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "24.0.6"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "wasmtime"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "25.0.0"
      }, {
        "fixed" : "36.0.6"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "wasmtime"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "37.0.0"
      }, {
        "fixed" : "40.0.4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-243v-98vx-264h"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-27572"
  }, {
    "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"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2026-0021.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-02-24T21:08:06Z",
    "nvd_published_at" : "2026-02-24T22:16:32Z"
  }
}