{"id":"CVE-2026-115889","state":"PUBLISHED","title":"Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation","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.","publishedAt":"2026-10-23T21:23:27.669Z","updatedAt":"2026-10-26T17:42:15.319Z","severity":{"score":9.9,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","source":"GitHub_M"},"assigner":"GitHub_M","products":["bytecodealliance wasmtime"],"affected":[{"vendor":"bytecodealliance","product":"wasmtime","versions":[{"version":"< 36.0.19","status":"affected"},{"version":">= 37.0.0, < 43.0.0","status":"affected"}]}],"references":["https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxm","https://github.com/bytecodealliance/wasmtime/pull/12613","https://github.com/bytecodealliance/wasmtime/pull/14818","https://github.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d03f4a438dae0","https://github.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8cc0c9f11e56aa","https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19","https://github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0"],"weaknesses":["CWE-197","CWE-843"],"ingestedAt":"2026-10-29T20:10:43.281Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/115xxx/CVE-2026-115889.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-115889","state":"PUBLISHED","datePublished":"2026-10-23T21:23:27.669Z","dateUpdated":"2026-10-26T17:42:15.319Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-10-23T19:37:27.176Z"},"containers":{"cna":{"title":"Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation","descriptions":[{"lang":"en","value":"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":[{"vendor":"bytecodealliance","product":"wasmtime","versions":[{"version":"< 36.0.19","status":"affected"},{"version":">= 37.0.0, < 43.0.0","status":"affected"}]}],"references":[{"url":"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxm","name":"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxm","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/bytecodealliance/wasmtime/pull/12613","name":"https://github.com/bytecodealliance/wasmtime/pull/12613","tags":["x_refsource_MISC"]},{"url":"https://github.com/bytecodealliance/wasmtime/pull/14818","name":"https://github.com/bytecodealliance/wasmtime/pull/14818","tags":["x_refsource_MISC"]},{"url":"https://github.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d03f4a438dae0","name":"https://github.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d03f4a438dae0","tags":["x_refsource_MISC"]},{"url":"https://github.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8cc0c9f11e56aa","name":"https://github.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8cc0c9f11e56aa","tags":["x_refsource_MISC"]},{"url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19","name":"https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19","tags":["x_refsource_MISC"]},{"url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0","name":"https://github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":9.9,"baseSeverity":"CRITICAL","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"LOW","scope":"CHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-197","lang":"en","description":"CWE-197: Numeric Truncation Error","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-843","lang":"en","description":"CWE-843: Access of Resource Using Incompatible Type ('Type Confusion')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-10-23T21:23:27.669Z"},"source":{"advisory":"GHSA-897f-g5gm-fmxm","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-26T15:40:36.390562Z","id":"CVE-2026-115889","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-26T17:42:15.319Z"}}]}}}