Resource exhaustion in Bytecodealliance Wasmtime
CVE-2026-27572
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 · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.007 (51.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 51.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.007 · change: +0.002
Affected products
- Bytecodealliance Wasmtime — versions < 24.0.6, >= 25.0.0, < 36.0.6, >= 37.0.0, < 40.0.4
Weakness classification (CWE)
References
- github.com/bytecodealliance/wasmtime/security/advisories/GHSA-243v-98vx-264h (Third Party Advisory)
- github.com/bytecodealliance/wasmtime/commit/301dc7162cca51def19131019af1187f459… (Patch)
- docs.rs/http/1.4.0/http/header/ (Not Applicable)
- github.com/bytecodealliance/wasmtime/releases/tag/v24.0.6 (Product, Release Notes)
- github.com/bytecodealliance/wasmtime/releases/tag/v36.0.6 (Product, Release Notes)
- github.com/bytecodealliance/wasmtime/releases/tag/v40.0.4 (Product, Release Notes)
- github.com/bytecodealliance/wasmtime/releases/tag/v41.0.4 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-27572?
- CVE-2026-27572 is a high-severity vulnerability in Bytecodealliance Wasmtime, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2026-02-24.
- How severe is CVE-2026-27572?
- High severity. CVSS v3 base score is 7.5 out of 10.