Medium severity · published Mar 11, 2026
CVE-2026-31859
Craft has Reflective XSS via incomplete return URL sanitization
6.1
CVSS
0.2%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 8% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CM
cms · craftcms
>= 4.15.3, < 4.17.3; >= 5.7.5, < 5.9.7 · source: vendor
CC
Craft Cms · Craftcms
4.15.3 before 4.17.3; 5.7.5 before 5.9.7 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-31859
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-31859
Patch
https://github.com/craftcms/cms/security/advisories/GHSA-fvwq-45qv-xvhv
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