{"id":"CVE-2026-115889","title":"Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation","summary":"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…","severity":"critical","cvss":9.9,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","cvssSource":"cna","cwe":["CWE-197","CWE-843"],"vendor":"bytecodealliance","product":"wasmtime","affected":["wasmtime < 36.0.19","wasmtime >= 37.0.0, < 43.0.0"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-26T15:40:36.390562Z"},"published":"2026-10-23","updated":"2026-10-26","sourceUpdated":"2026-10-26T17:42:15.319Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-115889","references":[{"url":"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxm","label":"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxm"},{"url":"https://github.com/bytecodealliance/wasmtime/pull/12613","label":"https://github.com/bytecodealliance/wasmtime/pull/12613"},{"url":"https://github.com/bytecodealliance/wasmtime/pull/14818","label":"https://github.com/bytecodealliance/wasmtime/pull/14818"},{"url":"https://github.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d03f4a438dae0","label":"https://github.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d03f4a438dae0"},{"url":"https://github.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8cc0c9f11e56aa","label":"https://github.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8cc0c9f11e56aa"},{"url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19","label":"https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19"},{"url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0","label":"https://github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0"},{"url":"https://crates.io/crates/wasmtime"},{"url":"https://rustsec.org/advisories/RUSTSEC-2026-0380.html"},{"url":"https://github.com/bytecodealliance/wasmtime"},{"url":"https://github.com/advisories/GHSA-897f-g5gm-fmxm"}],"tags":["cve.org","osv","rust","ghsa"],"epss":0.00454,"epssPercentile":0.39227,"aliases":["RUSTSEC-2026-0380","GHSA-897f-g5gm-fmxm"],"ecosystem":"rust","patched":["wasmtime 43.0.0"],"ingestedAt":"2026-10-23T21:38:13.047Z","slug":"CVE-2026-115889","body":"## Overview\n\nWasmtime 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.\n\n## Affected\n\n- `wasmtime < 36.0.19`\n- `wasmtime >= 37.0.0, < 43.0.0`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Package advisory (CVE-2026-115889)\n\nAffected packages:\n\n- `wasmtime >= 37.0.0, < 43.0.0`\n\nPatched in:\n\n- `wasmtime 43.0.0`\n\nSource: https://osv.dev/vulnerability/RUSTSEC-2026-0380","depth":"midnight","depthScore":55,"depthScoreParts":{"impact":54.5,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}