PYSEC-2026-1385
Flask-CORS allows for inconsistent CORS matching
Quick fix
PYSEC-2026-1385 — flask-cors: upgrade to the fixed version with the command below.
pip install --upgrade 'flask-cors>=6.0.0'Details
A vulnerability in corydolphin/flask-cors version 5.0.1 allows for inconsistent CORS matching due to the handling of the '+' character in URL paths. The request.path is passed through the unquote_plus function, which converts the '+' character to a space ' '. This behavior leads to incorrect path normalization, causing potential mismatches in CORS configuration. As a result, endpoints may not be matched correctly to their CORS settings, leading to unexpected CORS policy application. This can cause unauthorized cross-origin access or block valid requests, creating security vulnerabilities and usability issues.
Are you affected?
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Affected packages
References
- https://nvd.nist.gov/vuln/detail/CVE-2024-6844[ADVISORY]
- https://github.com/corydolphin/flask-cors/commit/35d875319621bd129a38b2b823abf4a2f6cda536[WEB]
- https://github.com/corydolphin/flask-cors[PACKAGE]
- https://github.com/corydolphin/flask-cors/blob/main/flask_cors/extension.py#L193[WEB]
- https://huntr.com/bounties/731a6cd4-d05f-4fe6-8f5b-fe088d7b34e0[WEB]
- https://lists.debian.org/debian-lts-announce/2025/05/msg00049.html[WEB]
- https://pypi.org/project/flask-cors[PACKAGE]
- https://github.com/advisories/GHSA-8vgw-p6qm-5gr7[ADVISORY]