{"id":"CVE-2026-47261","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-47261","generatedAt":"2026-10-28T01:45:40.039Z","title":"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…","description":"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":"2026-06-15T21:17:11.000Z","lastModified":"2026-10-25T23:10:00.000Z","status":"Analyzed","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","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"},"cwe":["CWE-284"],"affected":["bytecodealliance/wasmtime"],"epss":{"score":0.00357,"percentile":0.29205,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.36%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v24.0.9","tags":["Release Notes"],"source":"security-advisories@github.com"},{"url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.10","tags":["Release Notes"],"source":"security-advisories@github.com"},{"url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v44.0.2","tags":["Release Notes"],"source":"security-advisories@github.com"},{"url":"https://github.com/bytecodealliance/wasmtime/releases/tag/v45.0.0","tags":["Release Notes"],"source":"security-advisories@github.com"},{"url":"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-2r75-cxrj-cmph","tags":["Mitigation","Vendor Advisory"],"source":"security-advisories@github.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-47261","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}