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GHSA-243v-98vx-264h

Wasmtime can panic when adding excessive fields to a `wasi:http/types.fields` instance

Source: GitHub Advisory Database (reviewed) Moderate CVE-2026-27572

Packages

EcosystemPackageAffectedFixed in
crates.io wasmtime < 24.0.6 24.0.6
crates.io wasmtime >= 25.0.0, < 36.0.6 36.0.6
crates.io wasmtime >= 37.0.0, < 40.0.4 40.0.4

Details

As written in the advisory (Markdown source, shown as plain text).

### 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)

References

External links from the advisory. They lead to third-party sites.