Flask-Security has an Open Redirect issue

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.7 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Open Redirect in Flask-Security Summary flasksecurity.utils.validateredirecturl() can allow an attacker-controlled redirect URL when subdomain redirects are enabled. The bypass uses a backslash inside the URL authority/host: Python's urlsplit() parses the full authority as evil.com\.whitelist.com or evil.com%5C.whitelist.com. Because the value ends with .whitelist.com, validateredirecturl() accepts it as an allowed subdomain of whitelist.com. This is similar in class to the previous Flask-Security-Too open redirect advisory CVE-2023-49438 / GHSA-672h-6x89-76m5, where crafted redirect URLs bypassed validation through browser URL normalization behavior. Affected Configuration The issue requires subdomain redirects to be enabled: Tested environment: Impact An attacker can craft a URL that passes Flask-Security's redirect validation and produces a 302 response to an attacker-controlled URL-like authority. This can be used for phishing or other attacks that rely on a trusted application…

Published by the source

23 Jun 2026, 22:46 UTC

Last modified by the source

23 Jun 2026, 23:00 UTC

Source last checked

26 Oct 2026, 13:46 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-w2j7-f3c6-g8cw

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-w2j7-f3c6-g8cw

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# Patch Next advisory brief: GHSA-w2j7-f3c6-g8cw

Advisory: Flask-Security has an Open Redirect issue
IDs: GHSA-w2j7-f3c6-g8cw
Record: https://patchnext.com/advisories/ghsa-w2j7-f3c6-g8cw (revision 2, source checked 26 Oct 2026, 13:46 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: flask-security 5.8.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI flask-security: affected <= 5.8.0; fixed in 5.8.1

## Suggested inspection (read-only)
- `python -m pip show flask-security`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on flask-security.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-w2j7-f3c6-g8cw (OSV record GHSA-w2j7-f3c6-g8cw lists affected ranges: PyPI flask-security >=0 <5.8.1 (fixed))
- Verified: https://github.com/advisories/GHSA-w2j7-f3c6-g8cw (GitHub-reviewed advisory GHSA-w2j7-f3c6-g8cw lists affected ranges: PyPI flask-security >=0 <=5.8.0)

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