What is CVE-2026-35055?

CVE-2026-35055 is a medium-severity vulnerability in Xenforo, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-04-01.

How severe is CVE-2026-35055?

Medium severity. CVSS v3 base score is 6.1 out of 10.

XSS in Xenforo

CVE-2026-35055

XenForo before 2.3.9 and before 2.2.18 is vulnerable to cross-site scripting (XSS) related to lightbox usage in posts. An attacker can inject malicious scripts that execute when users interact with post content displayed in the lightbox.

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.000 (10.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

Affected products

Xenforo — versions 2.3.0, 0

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

XenForo 2.3.9 (inc XFMG) & 2.2.18 Released (Security Fix) (vendor-advisory, patch)
VulnCheck Advisory: XenForo Cross-Site Scripting via Lightbox in Posts (third-party-advisory)

Frequently asked questions

What is CVE-2026-35055?: CVE-2026-35055 is a medium-severity vulnerability in Xenforo, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-04-01.
How severe is CVE-2026-35055?: Medium severity. CVSS v3 base score is 6.1 out of 10.