XSS in Getgrav Grav
CVE-2026-75834
Grav before 2.0.14 contains a stored cross-site scripting vulnerability in the Security::detectXss() function (system/src/Grav/Common/Security.php). All XSS detection patterns use the PCRE /u (UTF-8) modifier, so a single invalid UTF-8 byte anywhere in page content causes preg_match() to return false for every pattern, silently bypassing the save-time XSS safety gate (Validation::checkSafety()). An authenticated attacker with page-edit permissions (without the security.xss_whitelist privilege) can store malicious JavaScript that executes in the browser of a visitor who views the affected page.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (15.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 15th percentile — 15.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001
Affected products
Weakness classification (CWE)
References
- github.com/getgrav/grav/security/advisories/GHSA-q2j8-x8hf-63ch (vendor-advisory)
- www.vulncheck.com/advisories/grav-before-stored-xss-via-invalid-utf-8-byte (third-party-advisory)
Frequently asked questions
- What is CVE-2026-75834?
- CVE-2026-75834 is a medium-severity vulnerability in Getgrav Grav, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-08-18.
- How severe is CVE-2026-75834?
- Medium severity. CVSS v3 base score is 5.4 out of 10.