CVE-2026-31859

Craft has Reflective XSS via incomplete return URL sanitization

State: Published
Severity: 6.9 Medium
Published: Mar 11, 2026
Updated: Mar 12, 2026
Reserved: Mar 9, 2026

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.

Scores

CVSS	Score	Vector	Source
4.0	6.9 Medium	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N	GitHub_M

Weaknesses

CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-116 Improper Encoding or Escaping of Output

Affected Products

Product	Versions
cmscraftcms	>= 4.15.3, < 4.17.3Affected >= 5.7.5, < 5.9.7Affected

References

https://github.com/craftcms/cms/security/advisories/GHSA-fvwq-45qv-xvhv

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