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

- 種別: advisory
- 重大度: critical
- 関連技術: rust, wasmtime
- CVE: CVE-2026-115889
- 公開日時: 2026-10-23T22:02:20.000Z
- 情報源: GitHub Advisory Database (https://github.com/advisories/GHSA-897f-g5gm-fmxm)
- パーマリンク: https://vulnpulse.app/items/ghsa-ghsa-897f-g5gm-fmxm

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…