vulnerability / NVI-00004771 / Revision 4
Grav: Non constant time nonce comparison in Utils::verifyNonce() used for CSRF protection
GitHub lists this reviewed advisory for getgrav/grav. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
3.7 low
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
3.7 LOW (3.1)
disclosure@vulncheck.com severity; no combined Null risk score.
6.3 MEDIUM (4.0)
disclosure@vulncheck.com severity; no combined Null risk score.
0.216%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.12082. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
getgrav/grav
source listed<= 2.0.15
## Summary `Grav\Common\Utils::verifyNonce()`, the core function Grav and its plugins use to validate CSRF nonces, compares the submitted nonce to the expected value with PHP's `===` operator instead of `hash_equals()`. `===` on strings short circuits at the first differing byte, so the comparison time leaks how many leading bytes of a guess are correct. This is CWE-208, Observable Timing Discrepancy. The codebase already knows to avoid this pattern. `hash_equals()` is used for the equivalent purpose in four other places I found: `system/src/Grav/Common/Session.php`, `system/src/Grav/Framework/Cache/Adapter/FileCache.php`, `system/src/Grav/Common/Scheduler/Scheduler.php` (the webhook token check), and `system/src/Grav/Common/Scheduler/JobQueue.php`. `Utils::verifyNonce()` is the one place I found that still uses a plain equality check for a secret comparison. ## Affected product and version Product: Grav CMS, getgrav/grav Confirmed present in: 2.0.15, commit c2b46866857a93a0aa7048e7ed707ed3ed45dbc3 ## Affected code `system/src/Grav/Common/Utils.php`, lines 1512 to 1521: ```php public static function verifyNonce($nonce, $action) { //Safety check for multiple nonces if
getgrav/grav
source listedECOSYSTEM: introduced 0; fixed 2.0.16
## Summary `Grav\Common\Utils::verifyNonce()`, the core function Grav and its plugins use to validate CSRF nonces, compares the submitted nonce to the expected value with PHP's `===` operator instead of `hash_equals()`. `===` on strings short circuits at the first differing byte, so the comparison time leaks how many leading bytes of a guess are correct. This is CWE-208, Observable Timing Discrepancy. The codebase already knows to avoid this pattern. `hash_equals()` is used for the equivalent purpose in four other places I found: `system/src/Grav/Common/Session.php`, `system/src/Grav/Framework/Cache/Adapter/FileCache.php`, `system/src/Grav/Common/Scheduler/Scheduler.php` (the webhook token check), and `system/src/Grav/Common/Scheduler/JobQueue.php`. `Utils::verifyNonce()` is the one place I found that still uses a plain equality check for a secret comparison. ## Affected product and version Product: Grav CMS, getgrav/grav Confirmed present in: 2.0.15, commit c2b46866857a93a0aa7048e7ed707ed3ed45dbc3 ## Affected code `system/src/Grav/Common/Utils.php`, lines 1512 to 1521: ```php public static function verifyNonce($nonce, $action) { //Safety check for multiple nonces if
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. FIRST EPSS
- vendor patch
The original advisory lists fixed boundaries 2.0.16 for getgrav/grav. Confirm the publisher’s latest guidance.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
- NVD lastModified does not establish freshness of every associated CPE record.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-38p6-h87p-r4cg ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- GHSA-38p6-h87p-r4cg ↗
GitHub Advisory Database via OSV · vendor advisory
Observed . GitHub-origin advisory, CC-BY-4.0; OSV is an aggregate copy, not independent corroboration.
- CVE-2026-72701 ↗
NIST National Vulnerability Database · official catalog
Observed . This product uses data from the NVD API but is not endorsed or certified by the NVD.
- CVE-2026-72701 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 4 ·
Source facts changed; compare the preserved prior revision.
- Revision 3 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 2 ·
Source facts changed; compare the preserved prior revision.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.