CVE-2026-34945
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.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
wasmtimecrates.io | >= 25.0.0, < 36.0.7 | 36.0.7 |
wasmtimecrates.io | >= 37.0.0, < 42.0.2 | 42.0.2 |
wasmtimecrates.io | >= 43.0.0, < 43.0.1 | 43.0.1 |
Affected products
1- cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:*Range: >=25.0.0,<36.0.7
Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
4- github.com/advisories/GHSA-m9w2-8782-2946ghsaADVISORY
- github.com/bytecodealliance/wasmtime/security/advisories/GHSA-m9w2-8782-2946nvdVendor AdvisoryWEB
- nvd.nist.gov/vuln/detail/CVE-2026-34945ghsaADVISORY
- rustsec.org/advisories/RUSTSEC-2026-0086.htmlghsaWEB
News mentions
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