CVE-2026-34945
Medium · 6.5CVSS
6.5
EPSS
0.4%
Published
Apr 9, 2026
CISA due date
—
The record
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
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| crates.io | wasmtime | 0.0.0-0 | 36.0.7 |
| crates.io | wasmtime | 25.0.0 | 36.0.7 |
| crates.io | wasmtime | 37.0.0 | 42.0.2 |
| crates.io | wasmtime | 43.0.0 | 43.0.1 |
| openSUSE:Tumbleweed | tree-sitter | 0 | 0.26.8-1.1 |
Related vulnerabilities
- RUSTSEC-2026-0086 Host data leakage with 64-bit tables and Winch Same vulnerability
- CVE-2026-44216 Wasmtime is a runtime for WebAssembly. Also affects wasmtime
- RUSTSEC-2026-0114 Panic when allocating a table exceeding the size of the host's address space Also affects wasmtime
- CVE-2026-34988 Wasmtime is a runtime for WebAssembly. Also affects wasmtime
- CVE-2026-35195 Wasmtime is a runtime for WebAssembly. Also affects wasmtime
- CVE-2026-34987 Wasmtime is a runtime for WebAssembly. Also affects wasmtime
- CVE-2026-35186 Wasmtime is a runtime for WebAssembly. Also affects wasmtime
- CVE-2026-34971 Wasmtime is a runtime for WebAssembly. Also affects wasmtime