Quick answers
- Is CVE-2026-119136 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-119136 being exploited in the wild.
- How severe is CVE-2026-119136?
- Medium severity, with a CVSS score of 4.8, published 29 October 2026.
- Which products and versions are affected?
- Bytecode Alliance Wasmtime 42.0.0 before 48.0.6, 49.0.0 before 49.0.3.
- Is there a fix for CVE-2026-119136?
- Yes: fixed in Wasmtime 48.0.6, 49.0.3. Until then: If the store requires async entrypoints to be used (such as when async host functions are defined), the vulnerability will not manifest. Embedders using Wasmtime synchronously only are unaffected. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-119136 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-119136?
- Check whether you run Bytecode Alliance Wasmtime at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: Wasmtime 48.0.6, 49.0.3
If the store requires async entrypoints to be used (such as when async host functions are defined), the vulnerability will not manifest. Embedders using Wasmtime synchronously only are unaffected.
Technical details
Wasmtime's Store fails to properly validate that sync-style re-entry into WebAssembly is prohibited when async-style execution is active. This allows host code to trigger thread-unsafe movement of !Send types across thread boundaries during asynchronous function calls, resulting in runtime panics or memory unsoundness. The vulnerability requires deliberate host code patterns mixing async and sync entry points and cannot be triggered from guest WebAssembly code alone.
Affected products
- Bytecode Alliance Wasmtime 42.0.0 before 48.0.6, 49.0.0 before 49.0.3
Timeline
- 2026-10-29: disclosed