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.
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-9pvw-hwfg-92h5
https://github.com/bytecodealliance/wasmtime/releases/tag/v49.0.4
https://github.com/bytecodealliance/wasmtime/releases/tag/v48.0.7
https://github.com/bytecodealliance/wasmtime/pull/14827
https://github.com/bytecodealliance/wasmtime/pull/14820
https://github.com/bytecodealliance/wasmtime/pull/14819
https://github.com/bytecodealliance/wasmtime/commit/994549891c8a706cb4f2809f9d17b9f67b31e618
https://github.com/bytecodealliance/wasmtime/commit/48dacc76241f06088e79f3ce1b17642f2f7bf158
https://github.com/bytecodealliance/wasmtime/commit/222ff3a65dab9aa7011f8c246937751a0bac5abd
Published: 2026-10-23
Updated: 2026-10-23
Base Score: 5
Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:P
Severity: Medium
Base Score: 7.5
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Severity: High
Base Score: 5.7
Vector: 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
Severity: Medium