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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-115889
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-23 22:16:58 UTC
Updated2026-10-23 22:16:58 UTC
DescriptionWasmtime 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.

Risk And Classification

Primary CVSS: v3.1 9.9 CRITICAL from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Problem Types: CWE-197 | CWE-843 | CWE-197 CWE-197: Numeric Truncation Error | CWE-843 CWE-843: Access of Resource Using Incompatible Type ('Type Confusion')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary9.9CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
3.1CNADECLARED9.9CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Bytecodealliance Wasmtime affected < 36.0.19 Not specified
CNA Bytecodealliance Wasmtime affected >= 37.0.0, < 43.0.0 Not specified

References

ReferenceSourceLinkTags
github.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8c... [email protected] github.com
github.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d... [email protected] github.com
github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0 [email protected] github.com
github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19 [email protected] github.com
github.com/bytecodealliance/wasmtime/pull/14818 [email protected] github.com
github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-... [email protected] github.com
github.com/bytecodealliance/wasmtime/pull/12613 [email protected] github.com
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