# CVE-2026-119142: Wasmtime host panic in call_async Future drop

Source: https://junglewise.ai/threats/cve-2026-119142-wasmtime-46-0-0-before-48-0-6-and-49-0-0-before-49-0-3-contains  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-29. Updated: 2026-10-29  
License: CC BY 4.0 with a link back

CVE-2026-119142 · Severity: medium · CVSS 4.8 · Published 2026-10-29

Wasmtime is a WebAssembly runtime that executes untrusted code. A flaw in how it cleans up asynchronous function calls can cause the host application to crash (panic) if a pending call is cancelled before execution starts. An attacker running WebAssembly code could trigger this to cause a denial of service.

Technologies: [Bytecode Alliance Wasmtime](https://junglewise.ai/threats/technologies/bytecode-alliance-wasmtime). Vendors: [Bytecode Alliance](https://junglewise.ai/threats/vendors/bytecode-alliance).

## Quick answers

**Is CVE-2026-119142 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-119142 being exploited in the wild.

**How severe is CVE-2026-119142?** Medium severity, with a CVSS score of 4.8, published 29 October 2026.

**Which products and versions are affected?** Bytecode Alliance Wasmtime 46.0.0 before 48.0.6; 49.0.0 before 49.0.3.

**Is there a fix for CVE-2026-119142?** Yes: fixed in Wasmtime 48.0.6, 49.0.3. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-119142 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-119142?** 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

## Technical details

The vulnerability exists in the Drop implementation for Futures returned by TypedFunc::call_async. When a guest task has not yet started and the Future is dropped, the cleanup code searches only one of several possible locations for work items, returning an error that is unwrapped and escalated to a panic. The attack requires the ability to issue call_async requests that get cancelled before the guest task begins execution.

## Affected products

- Bytecode Alliance Wasmtime 46.0.0 before 48.0.6; 49.0.0 before 49.0.3

## Timeline

- 2026-10-14: disclosed
- 2026-10-29: advisory

## References

- [https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-3r89-v5mq-j5xf](https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-3r89-v5mq-j5xf)
- [https://www.vulncheck.com/advisories/wasmtime-46.0.0-before-48.0.6-and-49.0.0-before-49.0.3-host-panic-via-call-async-drop](https://www.vulncheck.com/advisories/wasmtime-46.0.0-before-48.0.6-and-49.0.0-before-49.0.3-host-panic-via-call-async-drop)

## Related threats

- [Wasmtime wasi-http response splitting via unvalidated headers](https://junglewise.ai/threats/cve-2026-121439-wasmtime-46-0-0-before-48-0-7-and-49-0-0-before-49-0-4-contains)
- [Wasmtime denial of service in component model stream operations](https://junglewise.ai/threats/cve-2026-119143-wasmtime-46-0-0-before-48-0-6-and-49-0-0-before-49-0-3-contains)
- [Wasmtime denial of service in realloc handling](https://junglewise.ai/threats/cve-2026-119141-wasmtime-46-0-0-before-48-0-6-and-49-0-0-before-49-0-3-contains)
- [Wasmtime denial of service via thread.yield in component start](https://junglewise.ai/threats/cve-2026-119140-wasmtime-46-0-0-before-48-0-6-and-49-0-0-before-49-0-3-contains)
- [Wasmtime host crash in async-lifted function invocation](https://junglewise.ai/threats/cve-2026-119139-wasmtime-46-0-0-before-48-0-6-and-49-0-0-before-49-0-3-contains)