Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation

影響: rust:wasmtime < 36.0.19 → 36.0.19, rust:wasmtime >= 37.0.0, < 43.0.0 → 43.0.0

In Wasmtime prior to v43, the Cranelift compiler backend bit-packs its SSA value indices in a way that can result in silent overflow in release builds, and result in incorrect value references in the IR resulting in arbitrary miscompilation. A very large Wasm function body, or one that is specially crafted to use many SSA values, can use this to force type-confusion or other arbitrary side-effects and escape the sandbox. Cranelift was changed in Wasmtime v43 to use a full u32 index, with checks…

Read on GitHub Advisory Database

On 10/24/2026, 07:02 AM, GitHub Advisory Database published "Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation" (type: Advisory). Severity is "Critical" (critical). Related technologies: Rust, Wasmtime / Wasmer. CVE: CVE-2026-115889.