Description
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 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. 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. There are no known workarounds at this time. Embedders are encouraged to update to a patched version of Wasmtime.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| bytecodealliance | wasmtime | < 24.0.6, >= 25.0.0, < 36.0.6, >= 37.0.0, < 40.0.4, >= 41.0.0, < 41.0.4 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | rust-wasmtime | 36.0.6+dfsg-1 | — |
| Debian 13 | rust-wasmtime | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | rust-wasmtime | No fix yet | — |
| Ubuntu 26.04 LTS | rust-wasmtime | No fix yet | — |
| Ubuntu 25.10 | rust-wasmtime | No fix yet | — |
| Ubuntu 24.04 LTS | rust-wasmtime | No fix yet | — |
Wolfi
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Wolfi rolling | wash | No fix yet | — |
| Wolfi rolling | wasmcloud | 2.0.1-r0 | — |
| Wolfi rolling | wizer | 10.0.0-r7 | — |
| Wolfi rolling | yara-x | 1.13.0-r2 | — |
| Wolfi rolling | zed | 0.228.0-r3 | — |
| Wolfi rolling | zellij | 0.44.0-r0 | — |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| crates.io | wasmtime | < 24.0.6 | 24.0.6 | GHSA-243v-98vx-264h |
| crates.io | wasmtime | >= 25.0.0, < 36.0.6 | 36.0.6 | GHSA-243v-98vx-264h |
| crates.io | wasmtime | >= 37.0.0, < 40.0.4 | 40.0.4 | GHSA-243v-98vx-264h |
| crates.io | wasmtime | >= 0.0.0-0, < 24.0.6 · >= 25.0.0, < 36.0.6 · >= 37.0.0, < 40.0.4 · >= 41.0.0, < 41.0.4 | 24.0.6, 36.0.6, 40.0.4, 41.0.4 | RUSTSEC-2026-0021 |
References
- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-243v-98vx-264h
- https://github.com/bytecodealliance/wasmtime/commit/301dc7162cca51def19131019af1187f45901c0a
- https://docs.rs/http/1.4.0/http/header/#limitations
- https://github.com/bytecodealliance/wasmtime/releases/tag/v24.0.6
- https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.6
- https://github.com/bytecodealliance/wasmtime/releases/tag/v40.0.4
- https://github.com/bytecodealliance/wasmtime/releases/tag/v41.0.4