{"id":"CVE-2021-23393","aliases":["GHSA-pjc4-3w99-j7v4","PYSEC-2021-96","SNYK-PYTHON-FLASKUNCHAINED-1293189"],"url":"https://o3.security/vulnerability/CVE-2021-23393","summary":"Open redirect in Flask-Unchained","details":"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.","published":"2021-06-11T00:15:09.273Z","modified":"2026-07-09T10:52:18.289365Z","cvss":{"score":5.4,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"PyPI","name":"flask-unchained","fixedVersion":"0.9.0"}],"fix":{"url":"https://github.com/briancappello/flask-unchained/commit/71e36b28166f9ffbe0a991f51127f0984f7e6a40","label":"briancappello/flask-unchained@71e36b2"},"references":[{"type":"FIX","url":"https://github.com/briancappello/flask-unchained/commit/71e36b28166f9ffbe0a991f51127f0984f7e6a40"},{"type":"FIX","url":"https://snyk.io/vuln/SNYK-PYTHON-FLASKUNCHAINED-1293189"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-09T10:52:18.289365Z"}}