Critical 9.9Published Oct 23, 2026

CVE-2026-115889Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation

Updated under an hour ago (Oct 28, 2026, 7:10 AM ET)

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It affects bytecodealliance wasmtime. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 0.45%, higher than 39% of scored CVEs.

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Every CVE for bytecodealliance wasmtime

Exploited in the last 30 days

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: 9.9 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Weakness (CWE): CWE-197, CWE-843
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 0.45% (percentile 39)
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Oct 26, 2026
First seen by InfoSec Signals: Oct 23, 2026

Affected products

Affected products

bytecodealliance wasmtime bytecodealliance:wasmtime (from the name)	before 36.0.19; from 37.0.0, < 43.0.0	CNA record

References

References

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

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.