PYSEC-2026-809

Vulnerability from pysec - Published: 2026-07-07 10:17 - Updated: 2026-07-07 11:30
VLAI
Details

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.

Severity
6.1 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Impacted products
Name purl
flask-security pkg:pypi/flask-security
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "flask-security",
        "purl": "pkg:pypi/flask-security"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5.5.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.2.0",
        "1.2.1",
        "1.2.2",
        "1.2.3",
        "1.5.0",
        "1.5.1",
        "1.5.2",
        "1.5.3",
        "1.5.4",
        "1.6.0",
        "1.6.1",
        "1.6.2",
        "1.6.3",
        "1.6.4",
        "1.6.5",
        "1.6.6",
        "1.6.7",
        "1.6.8",
        "1.6.9",
        "1.7.0",
        "1.7.1",
        "1.7.2",
        "1.7.3",
        "1.7.4",
        "1.7.5",
        "3.0.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2021-23385",
    "GHSA-cg8c-gc2j-2wf7"
  ],
  "details": "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 `\u0027autocorrect_location_header=False`.\n\n**Note:** Flask-Security is not maintained anymore.",
  "id": "PYSEC-2026-809",
  "modified": "2026-07-07T11:30:34.455732Z",
  "published": "2026-07-07T10:17:22.496909Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-23385"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/mattupstate/flask-security"
    },
    {
      "type": "WEB",
      "url": "https://security.snyk.io/vuln/SNYK-PYTHON-FLASKSECURITY-1293234"
    },
    {
      "type": "WEB",
      "url": "https://snyk.io/blog/url-confusion-vulnerabilities"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/flask-security"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-cg8c-gc2j-2wf7"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Flask-Security vulnerable to Open Redirect"
}



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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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