{"cve":"CVE-2021-23401","nvd":{"published":"2021-07-05T11:15:07.670","modified":"2026-06-17T03:38:41.707","status":"Modified","description":"This affects all versions of package Flask-User. When using the make_safe_url function, it is possible to bypass URL validation and redirect a user to an arbitrary URL by providing multiple back slashes such as /////evil.com/path or \\\\\\evil.com/path. This vulnerability is only exploitable if an alternative WSGI server other than Werkzeug is used, or the default behaviour of Werkzeug is modified using 'autocorrect_location_header=False.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","score":6.1},"cwes":["CWE-601"],"references":["https://github.com/lingthio/Flask-User","https://github.com/lingthio/Flask-User/blob/master/flask_user/user_manager__utils.py","https://snyk.io/vuln/SNYK-PYTHON-FLASKUSER-1293188","https://github.com/lingthio/Flask-User","https://github.com/lingthio/Flask-User/blob/master/flask_user/user_manager__utils.py"],"products":["flask-user_project:flask-user"],"source":"nvd","synced_at":"2026-10-19T21:20:07.141963181+00:00"},"epss":{"cve":"CVE-2021-23401","score":0.01113,"percentile":0.6601,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-4298-89hc-6rfv","url":"https://osv.dev/vulnerability/GHSA-4298-89hc-6rfv","summary":"Open Redirect in Flask-User","modified":"2024-09-20T18:22:30.355979Z","packages":[{"ecosystem":"PyPI","name":"flask-user","purl":"pkg:pypi/flask-user","ranges":["<=1.0.2.2"],"fixed":[]}]},{"id":"PYSEC-2021-337","url":"https://osv.dev/vulnerability/PYSEC-2021-337","summary":"","modified":"2023-11-08T04:05:07.511361Z","packages":[{"ecosystem":"PyPI","name":"flask-user","purl":"pkg:pypi/flask-user","ranges":["all versions"],"fixed":[]}]}],"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."]}