{"id":"PYSEC-2026-151","details":"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.","aliases":["CVE-2026-34983","GHSA-hfr4-7c6c-48w2","RUSTSEC-2026-0090"],"modified":"2026-05-21T15:00:24.330171463Z","published":"2026-04-09T19:16:24.850Z","references":[{"type":"ADVISORY","url":"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-hfr4-7c6c-48w2"}],"affected":[{"package":{"name":"wasmtime","ecosystem":"PyPI","purl":"pkg:pypi/wasmtime"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"43.0.0"}]}],"versions":["0.0.1","0.0.2","0.11.0","0.12.0","0.15.0","0.15.1","0.16.0","0.16.1","0.17.0","0.18.0","0.18.1","0.18.2","0.19.0","0.20.0","0.21.0","0.22.0","0.23.0","0.24.0","0.25.0","0.26.0","0.27.0","0.28.0","0.28.1","0.29.0","0.30.0","0.31.0","0.32.0","0.33.0","0.34.0","0.35.0","0.36.0","0.37.0","0.38.0","0.39.1","0.40.0","0.9.0","1.0.0","1.0.1","10.0.0","10.0.1","11.0.0","12.0.0","13.0.0","13.0.1","13.0.2","14.0.0","15.0.0","16.0.0","17.0.0","17.0.1","18.0.0","18.0.2","19.0.0","2.0.0","20.0.0","21.0.0","22.0.0","23.0.0","24.0.0","25.0.0","27.0.0","27.0.1","27.0.2","28.0.0","29.0.0","3.0.0","30.0.0","31.0.0","32.0.0","33.0.0","34.0.0","35.0.0","36.0.0","37.0.0","38.0.0","39.0.0","4.0.0","40.0.0","41.0.0","42.0.0","43.0.0","5.0.0","6.0.0","7.0.0","8.0.0","8.0.1","9.0.0"],"ecosystem_specific":{},"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/wasmtime/PYSEC-2026-151.yaml"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H"}]}