Wasmtime provides unsound API access to a WebAssembly shared linear memory

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2025-64345: 0.12% estimated exploitation activity in the next 30 days; percentile 1.63 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Wasmtime's Rust embedder API contains an unsound interaction where a WebAssembly shared linear memory could be viewed as a type which provides safe access to the host (Rust) to the contents of the linear memory. This is not sound for shared linear memories, which could be modified in parallel, and this could lead to a data race in the host. Wasmtime has a wasmtime::Memory type which represents linear memories in a WebAssembly module. Wasmtime also has wasmtime::SharedMemory, however, which represents shared linear memories introduced in the WebAssembly threads proposal. The API of SharedMemory does not provide accessors which return &[u8] in Rust, for example, as that's not a sound type signature when other threads could be modifying memory. The wasmtime::Memory type, however, does provide this API as it's intended to be used with non-shared memories where static knowledge is available that no concurrent or parallel reads or writes are happening. This means that it's not sound…

Published by the source

12 Nov 2025, 21:36 UTC

Last modified by the source

13 Nov 2025, 22:03 UTC

Source last checked

26 Oct 2026, 15:39 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-hc7m-r6v8-hg9q

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# Patch Next advisory brief: CVE-2025-64345

Advisory: Wasmtime provides unsound API access to a WebAssembly shared linear memory
IDs: CVE-2025-64345, GHSA-hc7m-r6v8-hg9q
Record: https://patchnext.com/advisories/cve-2025-64345 (revision 1, source checked 26 Oct 2026, 15:39 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 1.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: wasmtime 38.0.4, 37.0.3, 36.0.3, 24.0.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io wasmtime: affected >= 38.0.0, < 38.0.4; >= 37.0.0, < 37.0.3; >= 26.0.0, < 36.0.3; < 24.0.5; fixed in 24.0.5, 36.0.3, 38.0.4, 37.0.3

## Suggested inspection (read-only)
- crates.io wasmtime: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on wasmtime.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-hc7m-r6v8-hg9q (GitHub-reviewed advisory GHSA-hc7m-r6v8-hg9q lists affected ranges: crates.io wasmtime >=38.0.0 =37.0.0 =26.0.0 =0 <24.0.5)

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