by Kastro
Paper/Archive/CVE-2026-115889

CVE-2026-115889

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

EPSS 0.5%CVSS 9.9
critical.is priorityof 100
38
CVSS 9.9 (CNA)9.9 / 10 × 3029.7Not in CISA KEV+300.0EPSS percentile 39.4.394 × 207.9No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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

ProductAffectedFixed inSource
wasmtime< 36.0.19–CNA
wasmtime>= 37.0.0, < 43.0.0–CNA

Scores by source

GitHub_M (CNA)9.9CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
CISA ADPSSVCExploitation: none · Automatable: no · Technical impact: total

References

refgithub.com/bytecodealliance/wasmtime/pull/14818refgithub.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxmrefgithub.com/bytecodealliance/wasmtime/pull/12613refgithub.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d03f4a438dae0refgithub.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8cc0c9f11e56aarefgithub.com/bytecodealliance/wasmtime/releases/tag/v36.0.19refgithub.com/bytecodealliance/wasmtime/releases/tag/v43.0.0