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  5. CVE-2026-34943

CVE-2026-34943: Wasmtime has a possible panic when lifting `flags` component value

April 9, 2026 (updated April 24, 2026)

Wasmtime contains a possible panic which can happen when a flags-typed component model value is lifted with the Val type. If bits are set outside of the set of flags the component model specifies that these bits should be ignored but Wasmtime will panic when this value is lifted. This panic only affects wasmtime’s implementation of lifting into Val, not when using the flags! macro. This additionally only affects flags-typed values which are part of a WIT interface.

This has the risk of being a guest-controlled panic within the host which Wasmtime considers a DoS vector.

References

  • github.com/advisories/GHSA-m758-wjhj-p3jq
  • github.com/bytecodealliance/wasmtime
  • github.com/bytecodealliance/wasmtime/security/advisories/GHSA-m758-wjhj-p3jq
  • nvd.nist.gov/vuln/detail/CVE-2026-34943
  • rustsec.org/advisories/RUSTSEC-2026-0085.html

Code Behaviors & Features

Detect and mitigate CVE-2026-34943 with GitLab Dependency Scanning

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Affected versions

All versions before 24.0.7, all versions starting from 25.0.0 before 36.0.7, all versions starting from 37.0.0 before 42.0.2, all versions starting from 43.0.0 before 43.0.1, version 43.0.0

Fixed versions

  • 24.0.7
  • 36.0.7
  • 42.0.2
  • 43.0.1

Solution

Upgrade to versions 24.0.7, 36.0.7, 42.0.2, 43.0.1 or above.

Impact 7.5 HIGH

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

Learn more about CVSS

Weakness

  • CWE-248: Uncaught Exception

Source file

cargo/wasmtime/CVE-2026-34943.yml

Spotted a mistake? Edit the file on GitLab.

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