{"id":"CVE-2021-23385","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-23385","generatedAt":"2026-10-27T22:31:42.179Z","title":"When using the get_post_logout_redirect and get_post_login_redirect functions, 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.","description":"This affects all versions of package Flask-Security. When using the get_post_logout_redirect and get_post_login_redirect functions, 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. **Note:** Flask-Security is not maintained anymore.","published":"2022-08-02T14:15:10.000Z","lastModified":"2026-06-17T03:38:40.000Z","status":"Modified","sourceIdentifier":"report@snyk.io","cvss":{"version":"3.1","score":6.1,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"},"cwe":["CWE-601"],"affected":["flask-security project/flask-security"],"epss":{"score":0.01247,"percentile":0.69141,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (1.25%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://github.com/mattupstate/flask-security","tags":["Product","Third Party Advisory"],"source":"report@snyk.io"},{"url":"https://lists.debian.org/debian-lts-announce/2023/08/msg00034.html","source":"report@snyk.io"},{"url":"https://security.snyk.io/vuln/SNYK-PYTHON-FLASKSECURITY-1293234","tags":["Exploit","Third Party Advisory"],"source":"report@snyk.io"},{"url":"https://snyk.io/blog/url-confusion-vulnerabilities/","tags":["Technical Description","Third Party Advisory"],"source":"report@snyk.io"},{"url":"https://github.com/mattupstate/flask-security","tags":["Product","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2023/08/msg00034.html","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://security.snyk.io/vuln/SNYK-PYTHON-FLASKSECURITY-1293234","tags":["Exploit","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://snyk.io/blog/url-confusion-vulnerabilities/","tags":["Technical Description","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-23385","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}