{"id":"CVE-2025-66221","aliases":["GHSA-hgf8-39gv-g3f2","PYSEC-2026-2046"],"title":"Werkzeug safe_join() allows Windows special device names","summary":"Werkzeug safe_join() allows Windows special device names","severity":"medium","vendor":"werkzeug","product":"werkzeug","ecosystem":"pip","affected":["werkzeug < 3.1.4"],"patched":["werkzeug 3.1.4"],"published":"2025-12-02","updated":"2026-09-10","sourceUpdated":"2026-09-10T03:50:31.900494607Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-hgf8-39gv-g3f2","references":[{"url":"https://github.com/pallets/werkzeug/security/advisories/GHSA-hgf8-39gv-g3f2"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2025-66221"},{"url":"https://github.com/pallets/werkzeug/commit/4b833376a45c323a189cd11d2362bcffdb1c0c13"},{"url":"https://github.com/pallets/werkzeug"},{"url":"https://github.com/pallets/werkzeug/releases/tag/3.1.4"}],"tags":["osv","pip"],"epss":0.00511,"epssPercentile":0.42562,"ingestedAt":"2026-07-08T18:25:50.210Z","slug":"CVE-2025-66221","body":"## Overview\n\nWerkzeug's `safe_join` function allows path segments with Windows device names. On Windows, there are special device names such as `CON`, `AUX`, etc that are implicitly present and readable in every directory. `send_from_directory` uses `safe_join` to safely serve files at user-specified paths under a directory. If the application is running on Windows, and the requested path ends with a special device name, the file will be opened successfully, but reading will hang indefinitely.\n\n## Affected packages\n\n- `werkzeug < 3.1.4`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `werkzeug 3.1.4`","depth":"sunlit","depthScore":28,"depthScoreParts":{"impact":27.5,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}