Grav CMS before 2.0.16 contains a timing vulnerability in Utils::verifyNonce() that uses non-constant-time string comparison with the === operator instead of hash_equals() for CSRF nonce validation. Attackers can measure response timing differences to recover valid nonce values byte-by-byte through multiple requests, weakening CSRF protection below its intended security margin.
https://www.vulncheck.com/advisories/grav-cms-before-timing-attack-via-verifynonce
https://github.com/getgrav/grav/security/advisories/GHSA-38p6-h87p-r4cg
Published: 2026-08-25
Updated: 2026-08-27
Base Score: 2.6
Vector: CVSS2#AV:N/AC:H/Au:N/C:N/I:P/A:N
Severity: Low
Base Score: 3.7
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Severity: Low
Base Score: 6.3
Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Severity: Medium
EPSS: 0.00179