How severe is CVE-2026-31859?

CVE-2026-31859 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2026-31859 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (8th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-31859?

CVE-2026-31859 affects Craftcms Craft Cms. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-31859?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-31859 have an EU (EUVD) identifier?

Yes. CVE-2026-31859 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11261.

When was CVE-2026-31859 published?

CVE-2026-31859 was published on 2026-03-11 and last updated on 2026-06-17.

CVE-2026-31859

CVE-2026-31859 is a medium-severity vulnerability in Craftcms Craft Cms with a CVSS 3.x base score of 6.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
CVSS v4: 6.9
EPSS exploit prediction: 0% (8th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-11261
Weakness: CWE-79
Affected product: Craftcms Craft Cms
Published: 2026-03-11
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-31859?: 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.
How severe is CVE-2026-31859?: CVE-2026-31859 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-31859 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (8th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-31859?: CVE-2026-31859 affects Craftcms Craft Cms. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-31859?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-31859 have an EU (EUVD) identifier?: Yes. CVE-2026-31859 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11261.
When was CVE-2026-31859 published?: CVE-2026-31859 was published on 2026-03-11 and last updated on 2026-06-17.

References

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

Affected products (1)

cpe:2.3:a:craftcms:craft_cms:*:*:*:*:*:*:*:*

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