{"id":"CVE-2021-23385","aliases":["GHSA-cg8c-gc2j-2wf7","PYSEC-2026-809"],"title":"Flask-Security vulnerable to Open Redirect","summary":"Flask-Security vulnerable to Open Redirect","severity":"medium","cvss":6.1,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","vendor":"flask-security","product":"flask-security","ecosystem":"pip","affected":["flask-security <= 3.0.0"],"published":"2022-10-07","updated":"2026-07-07","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-cg8c-gc2j-2wf7","references":[{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-23385"},{"url":"https://github.com/mattupstate/flask-security"},{"url":"https://security.snyk.io/vuln/SNYK-PYTHON-FLASKSECURITY-1293234"},{"url":"https://snyk.io/blog/url-confusion-vulnerabilities"}],"tags":["osv","pip"],"epss":0.01147,"epssPercentile":0.65381,"ingestedAt":"2026-07-08T18:25:48.372Z","slug":"CVE-2021-23385","body":"## Overview\n\nThis 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`.\n\n**Note:** Flask-Security is not maintained anymore.\n\n## Affected packages\n\n- `flask-security <= 3.0.0`\n\n## Remediation\n\nRefer to the advisory for the patched release.","depth":"sunlit","depthScore":34,"depthScoreParts":{"impact":33.6,"likelihood":0.2,"exploitation":0,"ransomware":0},"changes":[]}