Out-of-bounds Read in Bytecodealliance Wasmtime
CVE-2026-34987
Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-…
Vulnerability class: Buffer Overflow
EPSS: 0.003 (19.9th percentile) — read the EPSS interpretation.
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.
Affected products
- Bytecodealliance Wasmtime — versions 43.0.0, >= 43.0.0, < 44.0.1, >= 25.0.0, < 36.0.7
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-34987?
- CVE-2026-34987 is a critical-severity vulnerability in Bytecodealliance Wasmtime, classified under Out-of-bounds Read. CVSS score: 9.9/10. Published 2026-04-09.
- How severe is CVE-2026-34987?
- Critical severity. CVSS v3 base score is 9.9 out of 10.