CVE-2025-64345: Bytecodealliance Wasmtime

Low severity, CVSS 1.8. EPSS: 0.1% chance of exploitation in the next 30 days.

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.

Affected products

• Bytecodealliance Wasmtime: from 38.0.1, before 38.0.4 (fixed in 38.0.4); from 37.0.0, before 37.0.3 (fixed in 37.0.3); from 26.0.0, before 36.0.3 (fixed in 36.0.3); before 24.0.5 (fixed in 24.0.5)

Published 2025-11-12. Last modified 2026-06-17.