Vulnerability Description
Craft is a content management system (CMS). The fix for CVE-2025-35939 in craftcms/cms introduced a strip_tags() call in src/web/User.php to sanitize return URLs before they are stored in the session. However, strip_tags() only removes HTML tags (angle brackets) -- it does not inspect or filter URL schemes. Payloads like javascript:alert(document.cookie) contain no HTML tags and pass through strip_tags() completely unmodified, enabling reflected XSS when the return URL is rendered in an href attribute. This vulnerability is fixed in 5.9.7 and 4.17.3.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Craftcms | Craft Cms | >= 4.15.3, < 4.17.3 |
Related Weaknesses (CWE)
References
- https://github.com/craftcms/cms/security/advisories/GHSA-fvwq-45qv-xvhvPatchVendor Advisory
FAQ
What is CVE-2026-31859?
CVE-2026-31859 is a vulnerability with a CVSS score of 6.1 (MEDIUM). Craft is a content management system (CMS). The fix for CVE-2025-35939 in craftcms/cms introduced a strip_tags() call in src/web/User.php to sanitize return URLs before they are stored in the session....
How severe is CVE-2026-31859?
CVE-2026-31859 has been rated MEDIUM with a CVSS base score of 6.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-31859?
Check the references section above for vendor advisories and patch information. Affected products include: Craftcms Craft Cms.