Vulnerability in Bytecodealliance Wasmtime
CVE-2026-115889
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.9 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Bytecodealliance Wasmtime — versions < 36.0.19, >= 37.0.0, < 43.0.0
Weakness classification (CWE)
References
- github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxm
- github.com/bytecodealliance/wasmtime/pull/12613
- github.com/bytecodealliance/wasmtime/pull/14818
- github.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d03f4a43…
- github.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8cc0c9f11…
- github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19
- github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0
Frequently asked questions
- What is CVE-2026-115889?
- CVE-2026-115889 is a critical-severity vulnerability in Bytecodealliance Wasmtime, classified under CWE-197. CVSS score: 9.9/10. Published 2026-10-23.
- How severe is CVE-2026-115889?
- Critical severity. CVSS v3 base score is 9.9 out of 10.