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 trigg
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.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | wasmtime | <= 43.0.0 | no fix |
References
- CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H- Weakness (CWE)
-- Platform
- Python (PyPI)
- Package
wasmtime- Disclosed
- 09.04.2026
- Updated
- 11.10.2026 12:19
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-151 - PyPA Advisory Database; CC BY 4.0
Vulnerability history: wasmtime
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 5
- First → latest
- 05.2021 04.2026
- Without a fix
- 3
- Exploited in attacks
- 0
Severity breakdown
- High 1
- Medium 3
- Low 1
Disclosures per year
- 2021: 2
- 2022: 0
- 2023: 0
- 2024: 2
- 2025: 0
- 2026: 1
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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 trigg this entry
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