Vulnerability details
CVE-2026-115889
bytecodealliance wasmtime
Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation
CVSS 3.1
9.9Critical
Official description
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.
CVSS scores
| Score | Version | Source | Vector |
|---|---|---|---|
| 9.9Critical | 3.1 | CVEProject cvelistV5 (CNA) (GitHub_M) | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H |
Affected products
| Vendor | Product | Versions | Source |
|---|---|---|---|
| bytecodealliance | wasmtime | < 36.0.19 | CVEProject cvelistV5 (CNA) |
| bytecodealliance | wasmtime | >= 37.0.0, < 43.0.0 | CVEProject cvelistV5 (CNA) |
References and advisories
7- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxm x_refsource_CONFIRM
- https://github.com/bytecodealliance/wasmtime/pull/12613 x_refsource_MISC
- https://github.com/bytecodealliance/wasmtime/pull/14818 x_refsource_MISC
- https://github.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d03f4a438dae0 x_refsource_MISC
- https://github.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8cc0c9f11e56aa x_refsource_MISC
- https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19 x_refsource_MISC
- https://github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0 x_refsource_MISC
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Details
- Published
- 2026-10-24
- Last updated
- 2026-10-26
- State
- Published
- Assigner (CNA)
- GitHub_M
- Kolun priority
- 25 · Low
Exploit prediction (EPSS)
0.45%
Probability of exploitation in 30 days
39.5%
Percentile (among all CVEs)
SSVC assessment (CISA)
- Automatable
- No
- Exploitation
- None
- Technical impact
- Total
Weaknesses (CWE)
- CWE-197Numeric Truncation Error
- CWE-843Access of Resource Using Incompatible Type ('Type Confusion')