GHSA-4x9g-vw65-vvf9
Fix: getgrav/grav@d9f9f03GHSA-4x9g-vw65-vvf9 is a CWE-770 vulnerability in getgrav/grav. O3 Security confirms whether GHSA-4x9g-vw65-vvf9 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Grav: Unauthenticated denial of service via unbounded image derivative dimensions
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-4x9g-vw65-vvf9.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
getgrav/grav🐘getgrav/gravReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Summary
An unauthenticated visitor exhausts server memory and CPU by requesting an image with oversized resize dimensions. One request drives a worker to several gigabytes of RAM and tens of seconds of CPU. A few concurrent requests take the host down.
Details
Grav::fallbackUrl() (system/src/Grav/Common/Grav.php:800-804) loops over every query parameter and, when the name matches ImageMedium::$magic_actions, calls that method on the medium with the comma-split value as arguments:
foreach ($uri->query(null, true) as $action => $params) {
if (in_array($action, ImageMedium::$magic_actions, true)) {
call_user_func_array([&$medium, $action], explode(',', $params));
}
}
forceResize runs with force=true, so it sets the output size to the attacker's values with no clamp against the source or any ceiling. The getgrav/image GD adapter then calls imagecreatetruecolor($w, $h). libgd allocates that buffer outside PHP's emalloc, so memory_limit does not cap it. Grav exposes no system.images.max_width/max_height setting.
PoC
Any page that serves an image works. With a 200x150 source image:
GET /home/test.png?forceResize=20000,20000
Measured on PHP 8.4.21 with memory_limit=128M:
- peak worker RSS 3,109 MB
- 21.9 s CPU
- HTTP 200, 1.6 MB response
8000x8000 already needs ~244 MB. The cache key includes the dimensions, so varying them forces fresh work on every request.
Impact
Unauthenticated denial of service against any Grav site that serves images. No account, plugin, or non-default config required.
Fix
Clamp the request-derived dimensions before dispatch, behind a configurable cap. The image library is the wrong layer; bound the arguments at the request boundary.
--- a/system/src/Grav/Common/Grav.php
+++ b/system/src/Grav/Common/Grav.php
@@ public function fallbackUrl($path)
foreach ($uri->query(null, true) as $action => $params) {
if (in_array($action, ImageMedium::$magic_actions, true)) {
- call_user_func_array([&$medium, $action], explode(',', $params));
+ $args = explode(',', $params);
+ $max = (int) $config->get('system.images.max_dimension', 8000);
+ if ($max > 0
+ && in_array($action, ['resize', 'forceResize', 'cropResize', 'cropZoom', 'zoomCrop', 'crop'], true)) {
+ foreach ($args as $a) {
+ if (is_numeric($a) && (int) $a > $max) {
+ return false; // reject oversized derivative request
+ }
+ }
+ }
+ call_user_func_array([&$medium, $action], $args);
}
}
Document system.images.max_dimension (default 8000) so operators can tune it. A total-pixel ceiling (width * height) is a stricter alternative.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | getgrav/grav | ≥ 2.0.0-beta.1&&< 2.0.0-rc.8 | 2.0.0-rc.8 |
| 🐘Packagist | getgrav/grav | all versions | 1.7.53 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for getgrav/grav. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update getgrav/grav to 2.0.0-rc.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4x9g-vw65-vvf9 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-4x9g-vw65-vvf9 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-4x9g-vw65-vvf9. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-4x9g-vw65-vvf9 in your dependencies?
O3 detects GHSA-4x9g-vw65-vvf9 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.