Critical severity · published Oct 23, 2026
CVE-2026-115889
Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation
New
9.9
CVSS
0.5%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 39% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
WA
wasmtime · bytecodealliance
< 36.0.19; >= 37.0.0, < 43.0.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-115889
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-115889
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/pull/12613
github.com
https://github.com/bytecodealliance/wasmtime/pull/14818
github.com
https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19
github.com
https://github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0
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