Vulnerability · Published Feb 24, 2026 · Assigned by GitHub_M
CVE-2026-27572Wasmtime can panic when adding excessive fields to a `wasi:http/types.fields` instance
Medium 6.9
In plain English
A medium-severity resource allocation without limits in wasmtime from bytecodealliance. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 44% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:13 | rust-wasmtime | no fix listed | DEBIAN-CVE-2026-27572 |
| Debian:14 | rust-wasmtime | 36.0.6+dfsg-1 | DEBIAN-CVE-2026-27572 |
| Ubuntu:24.04:LTS | rust-wasmtime | no fix listed | UBUNTU-CVE-2026-27572 |
| Ubuntu:25.10 | rust-wasmtime | no fix listed | UBUNTU-CVE-2026-27572 |
| Ubuntu:26.04:LTS | rust-wasmtime | no fix listed | UBUNTU-CVE-2026-27572 |
| Ubuntu:26.10 | rust-wasmtime | no fix listed | UBUNTU-CVE-2026-27572 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| bytecodealliance | wasmtime | < 24.0.6>= 25.0.0, < 36.0.6>= 37.0.0, < 40.0.4>= 41.0.0, < 41.0.4 |
Weakness: CWE-770 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
References
- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-243v-98vx-264h x_refsource_CONFIRM
- https://github.com/bytecodealliance/wasmtime/commit/301dc7162cca51def19131019af1187f45901c0a x_refsource_MISC
- https://docs.rs/http/1.4.0/http/header/#limitations x_refsource_MISC
- https://github.com/bytecodealliance/wasmtime/releases/tag/v24.0.6 x_refsource_MISC
- https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.6 x_refsource_MISC
- https://github.com/bytecodealliance/wasmtime/releases/tag/v40.0.4 x_refsource_MISC
- https://github.com/bytecodealliance/wasmtime/releases/tag/v41.0.4 x_refsource_MISC