{"id":"CVE-2021-23401","aliases":["EUVD-2021-0089","GHSA-4298-89hc-6rfv","PYSEC-2021-337","SNYK-PYTHON-FLASKUSER-1293188"],"status":"published","title":"Open Redirect","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.","severity":{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N/E:P/RL:U/RC:C","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.01113,"percentile":0.66277,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-601"],"published":"2021-07-05T10:25:11Z","modified":"2026-06-17T03:38:41Z","affected":[{"source":"ghsa","ecosystem":"PyPI","package":"flask-user","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"1.0.2.2"}]}]},{"source":"osv","ecosystem":"PyPI","package":"flask-user","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"1.0.2.2"}]}],"versions":["0.3","0.3.1","0.3.2","0.3.3","0.3.4","0.3.5","0.3.6","0.3.7","0.3.8","0.4.0","0.4.1","0.4.2","0.4.3","0.4.4","0.4.5","0.4.6","0.4.7","0.4.8","0.4.9","0.5.0","0.5.1","0.5.2","0.5.3","0.5.4","0.5.5","0.6","0.6.1","0.6.10","0.6.12","0.6.13","0.6.14","0.6.15","0.6.16","0.6.17","0.6.19","0.6.2","0.6.20","0.6.21","0.6.3","0.6.4","0.6.5","0.6.6","0.6.7","0.6.8","0.6.9","1.0.1.1","1.0.1.2","1.0.1.3","1.0.1.4","1.0.1.5","1.0.2.0","1.0.2.1","1.0.2.2"]},{"source":"osv","ecosystem":"PyPI","package":"flask-user","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.3","0.3.1","0.3.2","0.3.3","0.3.4","0.3.5","0.3.6","0.3.7","0.3.8","0.4.0","0.4.1","0.4.2","0.4.3","0.4.4","0.4.5","0.4.6","0.4.7","0.4.8","0.4.9","0.5.0","0.5.1","0.5.2","0.5.3","0.5.4","0.5.5","0.6","0.6.1","0.6.10","0.6.12","0.6.13","0.6.14","0.6.15","0.6.16","0.6.17","0.6.19","0.6.2","0.6.20","0.6.21","0.6.3","0.6.4","0.6.5","0.6.6","0.6.7","0.6.8","0.6.9","1.0.1.1","1.0.1.2","1.0.1.3","1.0.1.4","1.0.1.5","1.0.2.0","1.0.2.1","1.0.2.2"]}],"products":[{"vendor":"flask-user_project","product":"flask-user"}],"references":[{"url":"https://snyk.io/vuln/SNYK-PYTHON-FLASKUSER-1293188","tags":["x_refsource_MISC","x_transferred","Third Party Advisory","web","advisory"]},{"url":"https://github.com/lingthio/Flask-User","tags":["x_refsource_MISC","x_transferred","Product","Third Party Advisory","package","web"]},{"url":"https://github.com/lingthio/Flask-User/blob/master/flask_user/user_manager__utils.py","tags":["x_refsource_MISC","x_transferred","Exploit","Third Party Advisory","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-23401","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-4298-89hc-6rfv","tags":["advisory"]},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/flask-user/PYSEC-2021-337.yaml","tags":["web"]}],"sources":{"cve":[{"id":"CVE-2021-23401","title":"Open Redirect","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.","status":"published","published":"2021-07-05T10:25:11.545Z","modified":"2024-09-16T17:15:15.113Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N/E:P/RL:U/RC:C","level":"medium","assessor":"cna"}],"updated_at":"2026-11-02T14:33:00.819444Z"}],"euvd":[{"id":"EUVD-2021-0089","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.","status":"published","published":"2021-07-05T10:25:11Z","modified":"2024-09-16T17:15:15Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N/E:P/RL:U/RC:C","level":"medium"}],"updated_at":"2026-11-03T00:55:43.899381Z"}],"ghsa":[{"id":"GHSA-4298-89hc-6rfv","title":"Open Redirect in Flask-User","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 backslashes 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`.","status":"published","published":"2021-08-09T20:44:32Z","modified":"2024-09-20T17:59:20Z","cvss":[{"version":"4.0","score":5.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"},{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-601"],"updated_at":"2026-11-02T14:38:04.690827Z"}],"nvd":[{"id":"CVE-2021-23401","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.","status":"published","published":"2021-07-05T11:15:07.67Z","modified":"2026-06-17T03:38:41.707Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N","level":"medium","assessor":"secondary"},{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"primary"},{"version":"2.0","score":5.8,"vector":"AV:N/AC:M/Au:N/C:P/I:P/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-601"],"updated_at":"2026-11-02T14:06:55.259633Z"}],"osv":[{"id":"GHSA-4298-89hc-6rfv","title":"Open Redirect in Flask-User","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 backslashes 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`.","status":"published","published":"2021-08-09T20:44:32Z","modified":"2024-09-20T18:22:30.355979Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N","level":"medium"},{"version":"4.0","score":5.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-601"],"updated_at":"2026-11-02T15:46:36.434231Z"},{"id":"PYSEC-2021-337","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.","status":"published","published":"2021-07-05T11:15:00Z","modified":"2023-11-08T04:05:07.511361Z","updated_at":"2026-11-02T15:52:52.682031Z"}]}}