GHSA-243v-98vx-264h

ghsaUSosv

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

view advisory published 2026-02-24Licence: CC-BY-4.0

### 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)

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describes (1)

Related CVEs.

IDseverity exploitable
CVE-2026-27572UShigh7.5—
Wasmtime is a runtime for WebAssembly. Prior to versions 24.0.6, 36.0.6, 4.0.04, 41.0.4, and 42.0.0, Wasmtime's implementation of the `wasi:http/types.fields` resource is susceptib…
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