GHSA-243v-98vx-264h
Wasmtime can panic when adding excessive fields to a `wasi:http/types.fields` instance
Details
### Impact
Wasmtime's implementation of the `wasi:http/types.fields` resource is susceptible to panics when too many fields are added to the set of headers. Wasmtime's implementation in the `wasmtime-wasi-http` crate is backed by a data structure which panics when it reaches excessive capacity and this condition was not handled gracefully in Wasmtime. Panicking in a WASI implementation is a Denial of Service vector for embedders and is treated as a security vulnerability in Wasmtime.
### Patches
Wasmtime 24.0.6, 36.0.6, 40.0.4, 41.0.4, and 42.0.0 patch this vulnerability and return a trap to the guest instead of panicking.
### Workarounds
There are no known workarounds at this time, embedders are encouraged to update to a patched version of Wasmtime.
### Resources
* [Limitations of `http::HeaderMap`](https://docs.rs/http/1.4.0/http/header/#limitations)
Are you affected?
Enter the version of the package you're using.
Affected packages
0Fixed in: 24.0.6Upgrade wasmtime to 24.0.6 or newer (ecosystem crates.io).
25.0.0Fixed in: 36.0.6Upgrade wasmtime to 36.0.6 or newer (ecosystem crates.io).
37.0.0Fixed in: 40.0.4Upgrade wasmtime to 40.0.4 or newer (ecosystem crates.io).
References
- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-243v-98vx-264h[WEB]
- https://nvd.nist.gov/vuln/detail/CVE-2026-27572[ADVISORY]
- https://github.com/bytecodealliance/wasmtime/commit/301dc7162cca51def19131019af1187f45901c0a[WEB]
- https://docs.rs/http/1.4.0/http/header/#limitations[WEB]
- https://github.com/bytecodealliance/wasmtime[PACKAGE]
- https://github.com/bytecodealliance/wasmtime/releases/tag/v24.0.6[WEB]
- https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.6[WEB]
- https://github.com/bytecodealliance/wasmtime/releases/tag/v40.0.4[WEB]
- https://github.com/bytecodealliance/wasmtime/releases/tag/v41.0.4[WEB]
- https://rustsec.org/advisories/RUSTSEC-2026-0021.html[WEB]