{"id":"CVE-2026-27572","aliases":["GHSA-243v-98vx-264h","RUSTSEC-2026-0021"],"url":"https://o3.security/vulnerability/CVE-2026-27572","summary":"Wasmtime can panic when adding excessive fields to a `wasi:http/types.fields` instance","details":"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.","published":"2026-02-24T21:31:50.186Z","modified":"2026-08-12T03:51:34.175536413Z","cvss":null,"epss":{"score":0.00466,"percentile":0.38281,"asOf":"2026-08-24"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"crates.io","name":"wasmtime","fixedVersion":"24.0.6"},{"ecosystem":"crates.io","name":"wasmtime","fixedVersion":"36.0.6"},{"ecosystem":"crates.io","name":"wasmtime","fixedVersion":"40.0.4"}],"fix":{"url":"https://github.com/bytecodealliance/wasmtime/commit/301dc7162cca51def19131019af1187f45901c0a","label":"bytecodealliance/wasmtime@301dc71"},"references":[{"type":"WEB","url":"https://docs.rs/http/1.4.0/http/header/#limitations"},{"type":"WEB","url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v24.0.6"},{"type":"WEB","url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.6"},{"type":"WEB","url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v40.0.4"},{"type":"WEB","url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v41.0.4"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27572.json"},{"type":"ADVISORY","url":"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-243v-98vx-264h"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27572"},{"type":"FIX","url":"https://github.com/bytecodealliance/wasmtime/commit/301dc7162cca51def19131019af1187f45901c0a"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:34.175536413Z"}}