{"id":"CVE-2026-47261","aliases":["GHSA-2r75-cxrj-cmph","RUSTSEC-2026-0149"],"url":"https://o3.security/vulnerability/CVE-2026-47261","summary":"Wasmtime: WASI path_open(TRUNCATE) bypasses `FilePerms::WRITE` host restriction","details":"Wasmtime is a runtime for WebAssembly. In versions prior to 24.0.9, 36.0.10, and 44.0.2, when a filesystem preopen is given DirPerms::all() and FilePerms::READ without FilePerms::WRITE, this access control mechanism can be bypassed via the wasip2 descriptor.open-at or wasip1 path_open interfaces by opening a file with only the OpenFlags::TRUNCATE oflag. The root cause is that the clause handling OpenFlags::TRUNCATE in crates/wasi/src/filesystem.rs (Dir::open_at, lines 967–969) did not set open_mode |= OpenMode::WRITE;, which is later used for the access control check against FilePerms to determine whether opening the file is permitted; the single-line fix adds that missing assignment, after which the affected calls correctly fail with error-code.not-permitted and ERRNO_PERM respectively. Only wasmtime-wasi embeddings that combine DirPerms::MUTATE with FilePerms::READ are affected by this bug. In particular, the Wasmtime project's wasmtime-cli's use of wasmtime-wasi is not affected, because it always sets FilePerms::all() for all preopens. This issue has been fixed in versions 24.0.9, 36.0.10 and44.0.2.","published":"2026-06-15T19:47:40.366Z","modified":"2026-08-12T03:51:31.300841236Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"},"epss":{"score":0.00357,"percentile":0.28465,"asOf":"2026-08-10"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"crates.io","name":"wasmtime-wasi","fixedVersion":"44.0.2"},{"ecosystem":"crates.io","name":"wasmtime-wasi","fixedVersion":"36.0.10"},{"ecosystem":"crates.io","name":"wasmtime-wasi","fixedVersion":"24.0.9"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v24.0.9"},{"type":"WEB","url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.10"},{"type":"WEB","url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v44.0.2"},{"type":"WEB","url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v45.0.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/47xxx/CVE-2026-47261.json"},{"type":"ADVISORY","url":"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-2r75-cxrj-cmph"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-47261"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:31.300841236Z"}}