{"cve":"CVE-2025-66221","nvd":{"published":"2025-11-29T03:16:00.050","modified":"2026-10-07T20:10:01.970","status":"Analyzed","description":"Werkzeug is a comprehensive WSGI web application library. Prior to version 3.1.4, Werkzeug'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. This issue has been patched in version 3.1.4.","cvss_v4":{"vector":"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","score":6.3},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","score":5.3},"cwes":["CWE-67"],"references":["https://github.com/pallets/werkzeug/commit/4b833376a45c323a189cd11d2362bcffdb1c0c13","https://github.com/pallets/werkzeug/releases/tag/3.1.4","https://github.com/pallets/werkzeug/security/advisories/GHSA-hgf8-39gv-g3f2"],"products":["palletsprojects:werkzeug"],"source":"nvd","synced_at":"2026-10-19T22:16:02.354564667+00:00"},"epss":{"cve":"CVE-2025-66221","score":0.00511,"percentile":0.43274,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-hgf8-39gv-g3f2","url":"https://osv.dev/vulnerability/GHSA-hgf8-39gv-g3f2","summary":"Werkzeug safe_join() allows Windows special device names","modified":"2026-09-10T03:50:31.900494607Z","packages":[{"ecosystem":"PyPI","name":"werkzeug","purl":"pkg:pypi/werkzeug","ranges":["<3.1.4"],"fixed":["3.1.4"]}]},{"id":"PYSEC-2026-2046","url":"https://osv.dev/vulnerability/PYSEC-2026-2046","summary":"Werkzeug safe_join() allows Windows special device names","modified":"2026-07-07T17:47:56.418201869Z","packages":[{"ecosystem":"PyPI","name":"werkzeug","purl":"pkg:pypi/werkzeug","ranges":["<3.1.4"],"fixed":["3.1.4"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}