CVE-2026-34983
Wasmtime is a runtime for WebAssembly. In 43.0.0, cloning a wasmtime::Linker is unsound and can result in use-after-free bugs. This bug is not controllable by guest Wasm programs. It can only be triggered by a specific sequence of embedder API calls made by the host. Specifically, the following steps must occur to trigger the bug clone a wasmtime::Linker, drop the original linker instance, use the new, cloned linker instance, resulting in a use-after-free. This vulnerability is fixed in 43.0.1.
- CVSS 4.0
- 1.0
CVSS:4.0/AV:P/AC:H/AT:P/PR:H/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N - CVSS 3.1
- 5.0
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H - EPSS
- 0.1% chance of exploitation in the next 30 days; higher than 1% of CVEs (scores of 2026-10-26)
- CWE
- CWE-416
- Published
- Modified
- Record from
- the NVD, synced
Affected
- bytecodealliance:wasmtime
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-hfr4-7c6c-48w2 | crates.io | wasmtime | >=43.0.0 <43.0.1 | 43.0.1 |
| PYSEC-2026-151 | PyPI | wasmtime | <=43.0.0 | no fix published |
| RUSTSEC-2026-0090 | crates.io | wasmtime | >=43.0.0 <43.0.1 | 43.0.1 |