CVE-2026-115889 — Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation
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 bui…
Published: 2026-10-23 · CVSS: 9.9 · CVSS 3.1
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.
Source: CVE Program · Revision 579bdbb49eb1eb1fa5d95ade849eb65300d4cb26