CVE-2026-115889

critical

Description

Wasmtime is a runtime for WebAssembly. Prior to 36.0.19 and 43.0.0, the Cranelift compiler backend bit-packs SSA value indices in a way that can silently overflow in release builds when compiling a sufficiently large or specially crafted Wasm function with many SSA values. The overflow can make Cranelift reference incorrect IR values, causing arbitrary miscompilation, type confusion, and other attacker-controlled effects that may escape the Wasm sandbox on any architecture using the default Cranelift backend. This issue is fixed in versions 36.0.19 and 43.0.0.

References

https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxm

https://github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0

https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19

https://github.com/bytecodealliance/wasmtime/pull/14818

https://github.com/bytecodealliance/wasmtime/pull/12613

https://github.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8cc0c9f11e56aa

https://github.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d03f4a438dae0

Details

Source: Mitre, NVD

Published: 2026-10-23

Updated: 2026-10-23

Risk Information

CVSS v2

Base Score: 9

Vector: CVSS2#AV:N/AC:L/Au:S/C:C/I:C/A:C

Severity: High

CVSS v3

Base Score: 9.9

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Severity: Critical