Vulnerability Description
Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime's Winch compiler contains a bug where a 64-bit table, part of the memory64 proposal of WebAssembly, incorrectly translated the table.size instruction. This bug could lead to disclosing data on the host's stack to WebAssembly guests. The host's stack can possibly contain sensitive data related to other host-originating operations which is not intended to be disclosed to guests. This bug specifically arose from a mistake where the return value of table.size was statically typed as a 32-bit integer, as opposed to consulting the table's index type to see how large the returned register could be. When combined with details about Wnich's ABI, such as multi-value returns, this can be combined to read stack data from the host, within a guest. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Bytecodealliance | Wasmtime | >= 25.0.0, < 36.0.7 |
Related Weaknesses (CWE)
References
FAQ
What is CVE-2026-34945?
CVE-2026-34945 is a vulnerability with a CVSS score of 6.5 (MEDIUM). Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime's Winch compiler contains a bug where a 64-bit table, part of the memory64 proposal of WebAssembly, in...
How severe is CVE-2026-34945?
CVE-2026-34945 has been rated MEDIUM with a CVSS base score of 6.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-34945?
Check the references section above for vendor advisories and patch information. Affected products include: Bytecodealliance Wasmtime.