Bug 2442485 (CVE-2026-27572)

Summary: CVE-2026-27572 wasmtime: Wasmtime: Denial of Service via excessive HTTP header fields
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in Wasmtime, a runtime for WebAssembly. This vulnerability allows an attacker to cause a Denial of Service (DoS) by sending an excessive number of HTTP header fields. The Wasmtime implementation of the `wasi:http/types.fields` resource does not gracefully handle this condition, leading to a system panic and making the application unavailable.
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Bug Depends On: 2442502, 2442503    
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Description OSIDB Bzimport 2026-02-24 22:02:12 UTC 
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.