Description
Wasmtime is a runtime for WebAssembly. From 46.0.0 until 48.0.7 and 49.0.4, lowering a host-created component-model stream or future into a guest can omit a required payload-type check after the value passes through guest code and returns through StreamAny, FutureAny, Val::Stream, Val::Future, or an equivalent typed reader. A malicious guest that controls exported function types or returned values can cause the host to pass the type-erased value to a guest expecting a different payload type, which panics the Wasmtime host. This issue is fixed in versions 48.0.7 and 49.0.4.
References9
- github.com/bytecodealliance/wasmtime/commit/222ff3a65dab9aa7011…
- github.com/bytecodealliance/wasmtime/commit/48dacc76241f06088e7…
- github.com/bytecodealliance/wasmtime/commit/994549891c8a706cb4f…
- github.com/bytecodealliance/wasmtime/pull/14819
- github.com/bytecodealliance/wasmtime/pull/14820
- github.com/bytecodealliance/wasmtime/pull/14827
- github.com/bytecodealliance/wasmtime/releases/tag/v48.0.7
- github.com/bytecodealliance/wasmtime/releases/tag/v49.0.4
- github.com/bytecodealliance/wasmtime/security/advisories/GHSA-9…
Metrics
- CVSS 4.0
-
5.7
MEDIUM
Score source: CNA
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 0% percentile: 38 · as of 8 November 2026
- CWE
- CWE-248CWE-843
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.