critical9.9
CVE-2026-115889
Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| rust | wasmtime | < 36.0.19 | 36.0.19 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-897f-g5gm-fmxm
- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxm
- https://github.com/bytecodealliance/wasmtime/pull/12613
- https://github.com/bytecodealliance/wasmtime/pull/14818
- https://github.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d03f4a438dae0
- https://github.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8cc0c9f11e56aa
- https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19
- https://github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0
- https://rustsec.org/advisories/RUSTSEC-2026-0380.html