Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation
CVE-2026-115889 is fixed in rust-wasmtime on 1 platform by DEBIAN-CVE-2026-115889 (version 36.0.20+dfsg-1), released November 3, 2026. It is not reported as exploited. Patch Radar priority: Urgent.
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.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| rust-wasmtime · Debian 14 | 36.0.20+dfsg-1 | DEBIAN-CVE-2026-115889 | Nov 3, 2026 |
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