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Vulnerabilities CVE-2026-75834

CVE-2026-75834

Medium
Open
TLP:CLEAR

Grav before 2.0.14 Stored XSS via Invalid UTF-8 Byte

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Description

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.

Details

CVSS Score
5.1
CVSS Vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Confidence
90%
Published
Aug 18, 2026
Last Modified
Aug 18, 2026
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