CVE-2026-72701: Grav CMS before 2.0.16 Timing Attack via verifyNonce
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 hashequals() 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.
Affected Software
Event History
Frequently Asked Questions
Which deployments are affected?
Grav CMS versions before 2.0.16 are affected. The vulnerable nonce validation is in Utils::verifyNonce().
What does an attacker need to exploit this issue?
The attacker can make multiple requests and measure response timing differences while testing nonce values. No privileges or user interaction are indicated by the supplied CVSS vector.
What is the practical security impact?
Timing measurements may allow recovery of valid CSRF nonce values one byte at a time, weakening the intended CSRF protection. The stated impact is integrity-only, with no confidentiality or availability impact.
How can the issue be remediated?
Upgrade Grav CMS to version 2.0.16 or later. The vulnerable behavior is the use of the non-constant-time === comparison rather than hash_equals() for nonce validation.