CVE-2026-115889
Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation
CVSS Score
9.9
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-197 CWE-843 |
| Vendor | bytecodealliance |
| Product | wasmtime |
| Published | Oct 23, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High
Affected Versions
bytecodealliance / wasmtime
< 36.0.19 >= 37.0.0, < 43.0.0
References
github.com: https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxm github.com: https://github.com/bytecodealliance/wasmtime/pull/12613 github.com: https://github.com/bytecodealliance/wasmtime/pull/14818 github.com: https://github.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d03f4a438dae0 github.com: https://github.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8cc0c9f11e56aa github.com: https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19 github.com: https://github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0