{"id":"CVE-2021-23393","aliases":["EUVD-2021-0088","GHSA-pjc4-3w99-j7v4","PYSEC-2021-96","SNYK-PYTHON-FLASKUNCHAINED-1293189"],"status":"published","title":"Open Redirect","description":"This affects the package Flask-Unchained before 0.9.0. When using the the _validate_redirect_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. 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":0.00716,"percentile":0.54098,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-601"],"published":"2021-06-10T23:20:10Z","modified":"2026-10-20T10:53:37Z","fixes":[{"ecosystem":"PyPI","package":"flask-unchained","fixed_in":["0.9.0"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"flask-unchained","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.9.0"}]}]},{"source":"osv","ecosystem":"PyPI","package":"flask-unchained","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.9.0"}]}],"versions":["0.1.2","0.1.3","0.1.4","0.1.5","0.1.6","0.2.0","0.2.1","0.2.2","0.3.0","0.3.1","0.3.2","0.4.0","0.4.1","0.4.2","0.5.0","0.5.1","0.6.0","0.6.1","0.6.2","0.6.3","0.6.4","0.6.5","0.6.6","0.7.0","0.7.1","0.7.2","0.7.3","0.7.4","0.7.5","0.7.6","0.7.7","0.7.8","0.7.9","0.8.0","0.8.1"]},{"source":"osv","ecosystem":"PyPI","package":"flask-unchained","ranges":[{"type":"GIT","events":[{"introduced":"0"},{"fixed":"71e36b28166f9ffbe0a991f51127f0984f7e6a40"}]},{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.9.0"}]}],"versions":["0.1.2","0.1.3","0.1.4","0.1.5","0.1.6","0.2.0","0.2.1","0.2.2","0.3.0","0.3.1","0.3.2","0.4.0","0.4.1","0.4.2","0.5.0","0.5.1","0.6.0","0.6.1","0.6.2","0.6.3","0.6.4","0.6.5","0.6.6","0.7.0","0.7.1","0.7.2","0.7.3","0.7.4","0.7.5","0.7.6","0.7.7","0.7.8","0.7.9","0.8.0","0.8.1"]}],"products":[{"vendor":"flask_unchained_project","product":"flask_unchained"}],"references":[{"url":"https://snyk.io/vuln/SNYK-PYTHON-FLASKUNCHAINED-1293189","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix","web","advisory"]},{"url":"https://github.com/briancappello/flask-unchained/commit/71e36b28166f9ffbe0a991f51127f0984f7e6a40","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-23393","tags":["advisory"]},{"url":"https://github.com/briancappello/flask-unchained/commit/2bfeedf1bc31df851cab8c66df0c432b10406aad","tags":["web"]},{"url":"https://github.com/advisories/GHSA-pjc4-3w99-j7v4","tags":["advisory"]},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/flask-unchained/PYSEC-2021-96.yaml","tags":["web"]}],"sources":{"cve":[{"id":"CVE-2021-23393","title":"Open Redirect","description":"This affects the package Flask-Unchained before 0.9.0. When using the the _validate_redirect_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. 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":"2021-06-10T23:20:10.252Z","modified":"2024-09-16T17:18:13.774Z","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-2021-0088","description":"This affects the package Flask-Unchained before 0.9.0. When using the the _validate_redirect_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. 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":"2021-06-10T23:20:10Z","modified":"2024-09-16T17:18:13Z","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":"2026-11-03T00:55:43.455642Z"}],"ghsa":[{"id":"GHSA-pjc4-3w99-j7v4","title":"Open redirect in Flask-Unchained","description":"This affects the package Flask-Unchained before 0.9.0. When using the the _validate_redirect_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. 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":"2021-06-15T15:56:59Z","modified":"2024-09-20T20:01:52Z","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":"2026-11-02T14:38:05.526697Z"}],"nvd":[{"id":"CVE-2021-23393","description":"This affects the package Flask-Unchained before 0.9.0. When using the the _validate_redirect_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. 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":"2021-06-11T00:15:09.273Z","modified":"2026-06-17T03:38:40.823Z","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":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":"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":"2026-11-02T14:06:54.439974Z"}],"osv":[{"id":"CVE-2021-23393","description":"This affects the package Flask-Unchained before 0.9.0. When using the the _validate_redirect_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. 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":"2021-06-11T00:15:09.273Z","modified":"2026-10-20T10:53:37.744010568Z","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"}],"updated_at":"2026-11-02T15:44:18.367807Z"},{"id":"GHSA-pjc4-3w99-j7v4","title":"Open redirect in Flask-Unchained","description":"This affects the package Flask-Unchained before 0.9.0. When using the the _validate_redirect_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. 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":"2021-06-15T15:56:59Z","modified":"2024-09-20T20:25:46.997207Z","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":"2026-11-02T15:46:53.244788Z"},{"id":"PYSEC-2021-96","description":"This affects the package Flask-Unchained before 0.9.0. When using the the _validate_redirect_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. 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":"2021-06-11T00:15:00Z","modified":"2023-11-08T04:05:07.026421Z","updated_at":"2026-11-02T15:52:53.449407Z"}]}}