{"id":"PYSEC-2026-2044","summary":" Werkzeug safe_join() allows Windows special device names with compound extensions","details":"Werkzeug's `safe_join` function allows path segments with Windows device names that have file extensions or trailing spaces. On Windows, there are special device names such as `CON`, `AUX`, etc that are implicitly present and readable in every directory. Windows still accepts them with any file extension, such as `CON.txt`, or trailing spaces such as `CON `.\n\nThis was previously reported as https://github.com/pallets/werkzeug/security/advisories/GHSA-hgf8-39gv-g3f2, but the fix failed to account for compound extensions such as `CON.txt.html` or trailing spaces. It also missed some additional special names.\n\n`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.","aliases":["CVE-2026-21860","GHSA-87hc-h4r5-73f7"],"modified":"2026-07-07T17:47:51.007375023Z","published":"2026-07-07T16:03:17.057343Z","references":[{"type":"WEB","url":"https://github.com/pallets/werkzeug/security/advisories/GHSA-87hc-h4r5-73f7"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-21860"},{"type":"WEB","url":"https://github.com/pallets/werkzeug/commit/7ae1d254e04a0c33e241ac1cca4783ce6c875ca3"},{"type":"PACKAGE","url":"https://github.com/pallets/werkzeug"},{"type":"PACKAGE","url":"https://pypi.org/project/werkzeug"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-87hc-h4r5-73f7"}],"affected":[{"package":{"name":"werkzeug","ecosystem":"PyPI","purl":"pkg:pypi/werkzeug"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.1.5"}]}],"versions":["0.1","0.10","0.10.1","0.10.2","0.10.3","0.10.4","0.11","0.11.1","0.11.10","0.11.11","0.11.12","0.11.13","0.11.14","0.11.15","0.11.2","0.11.3","0.11.4","0.11.5","0.11.6","0.11.7","0.11.8","0.11.9","0.12","0.12.1","0.12.2","0.13","0.14","0.14.1","0.15.0","0.15.1","0.15.2","0.15.3","0.15.4","0.15.5","0.15.6","0.16.0","0.16.1","0.2","0.3","0.3.1","0.4","0.4.1","0.5","0.5.1","0.6","0.6.1","0.6.2","0.7","0.7.1","0.7.2","0.8","0.8.1","0.8.2","0.8.3","0.9","0.9.1","0.9.2","0.9.3","0.9.4","0.9.5","0.9.6","1.0.0","1.0.0rc1","1.0.1","2.0.0","2.0.0rc1","2.0.0rc2","2.0.0rc3","2.0.0rc4","2.0.0rc5","2.0.1","2.0.2","2.0.3","2.1.0","2.1.1","2.1.2","2.2.0","2.2.0a1","2.2.1","2.2.2","2.2.3","2.3.0","2.3.1","2.3.2","2.3.3","2.3.4","2.3.5","2.3.6","2.3.7","2.3.8","3.0.0","3.0.1","3.0.2","3.0.3","3.0.4","3.0.5","3.0.6","3.1.0","3.1.1","3.1.2","3.1.3","3.1.4"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/werkzeug/PYSEC-2026-2044.yaml"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N"}]}