Wasmtime panic when pending calls are run after a trap

Severity: medium · CVSS 4 · Published 2026-10-14

Wasmtime is a WebAssembly runtime used to execute untrusted WebAssembly code in applications. A flaw in how Wasmtime handles pending function calls after a trap (WebAssembly exception) can cause the runtime to panic and crash, disrupting service availability for applications relying on it.

Technologies: Bytecode Alliance Wasmtime, wasmtime (crates.io). Vendors: Bytecode Alliance, crates.io.

Quick answers

Is This vulnerability exploited in the wild?
No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.
How severe is This vulnerability?
Medium severity, with a CVSS score of 4, published 14 October 2026.
Which products and versions are affected?
Bytecode Alliance Wasmtime 46.0.0 through 48.0.5, 49.0.0 through 49.0.2; wasmtime (crates.io) SEMVER:introduced=46.0.0,fixed=48.0.6,introduced=49.0.0,fixed=49.0.3.
Is there a fix for This vulnerability?
Yes. wasmtime (crates.io): upgrade to 49.0.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is This vulnerability attacked?
It is attacked over the network, in a software library.
Am I affected?
Check whether you run Bytecode Alliance Wasmtime or wasmtime (crates.io) 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

  • wasmtime (crates.io): upgrade to 49.0.3 or later
    cargo update -p wasmtime

Technical details

A panic occurs in Wasmtime when pending calls are executed after a trap has been triggered. The vulnerability is a denial-of-service condition affecting the host runtime. Exploitation requires prior authentication and active user interaction with the vulnerable system.

Affected products

  • Bytecode Alliance Wasmtime 46.0.0 through 48.0.5, 49.0.0 through 49.0.2

Identifiers

  • GHSA-hmwq-g22x-qjw5
  • RUSTSEC-2026-0361

Timeline

  • 2026-10-14: disclosed
  • 2026-10-14: patched

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.