CVE-2026-31859 MEDIUM

CVE-2026-31859: Craft has Reflective XSS via incomplete return URL sanitization

Vendor Craftcms
Product cms
Weakness CWE-79 · XSS
Published March 11, 2026
Last update March 12, 2026
View on NVD All CVEs

CVSS base score

6.9/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality —
Integrity —

CVSS vector

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

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

March 11, 2026 CVE published
March 12, 2026 Record updated