{"id":"GHSA-4x9g-vw65-vvf9","summary":"Grav: Unauthenticated denial of service via unbounded image derivative dimensions","details":"### Summary\nAn 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.\n\n### Details\n`Grav::fallbackUrl()` (system/src/Grav/Common/Grav.php:800-804) loops over every query parameter and, when the name matches `ImageMedium::$magic_actions`, calls that method on the medium with the comma-split value as arguments:\n\n```php\nforeach ($uri-\u003equery(null, true) as $action =\u003e $params) {\n    if (in_array($action, ImageMedium::$magic_actions, true)) {\n        call_user_func_array([&$medium, $action], explode(',', $params));\n    }\n}\n```\n\n`forceResize` runs with `force=true`, so it sets the output size to the attacker's values with no clamp against the source or any ceiling. The `getgrav/image` GD adapter then calls `imagecreatetruecolor($w, $h)`. libgd allocates that buffer outside PHP's `emalloc`, so `memory_limit` does not cap it. Grav exposes no `system.images.max_width`/`max_height` setting.\n\n### PoC\nAny page that serves an image works. With a 200x150 source image:\n\n```\nGET /home/test.png?forceResize=20000,20000\n```\n\nMeasured on PHP 8.4.21 with `memory_limit=128M`:\n\n- peak worker RSS 3,109 MB\n- 21.9 s CPU\n- HTTP 200, 1.6 MB response\n\n`8000x8000` already needs ~244 MB. The cache key includes the dimensions, so varying them forces fresh work on every request.\n\n### Impact\nUnauthenticated denial of service against any Grav site that serves images. No account, plugin, or non-default config required.\n\n## Fix\nClamp the request-derived dimensions before dispatch, behind a configurable cap. The image library is the wrong layer; bound the arguments at the request boundary.\n\n```diff\n--- a/system/src/Grav/Common/Grav.php\n+++ b/system/src/Grav/Common/Grav.php\n@@ public function fallbackUrl($path)\n                 foreach ($uri-\u003equery(null, true) as $action =\u003e $params) {\n                     if (in_array($action, ImageMedium::$magic_actions, true)) {\n-                        call_user_func_array([&$medium, $action], explode(',', $params));\n+                        $args = explode(',', $params);\n+                        $max = (int) $config-\u003eget('system.images.max_dimension', 8000);\n+                        if ($max \u003e 0\n+                            && in_array($action, ['resize', 'forceResize', 'cropResize', 'cropZoom', 'zoomCrop', 'crop'], true)) {\n+                            foreach ($args as $a) {\n+                                if (is_numeric($a) && (int) $a \u003e $max) {\n+                                    return false; // reject oversized derivative request\n+                                }\n+                            }\n+                        }\n+                        call_user_func_array([&$medium, $action], $args);\n                     }\n                 }\n```\n\nDocument `system.images.max_dimension` (default 8000) so operators can tune it. A total-pixel ceiling (`width * height`) is a stricter alternative.","aliases":["CVE-2026-53653"],"modified":"2026-08-14T19:30:08.179015553Z","published":"2026-08-14T19:23:38Z","database_specific":{"github_reviewed_at":"2026-08-14T19:23:38Z","nvd_published_at":"2026-07-10T17:16:57Z","cwe_ids":["CWE-770"],"severity":"HIGH","github_reviewed":true},"references":[{"type":"WEB","url":"https://github.com/getgrav/grav/security/advisories/GHSA-4x9g-vw65-vvf9"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53653"},{"type":"WEB","url":"https://github.com/getgrav/grav/commit/d9f9f0369a07ae5c96cde700c7949e1237b29cf6"},{"type":"WEB","url":"https://github.com/getgrav/grav/commit/f4c0f42eea755cedad6f626b342c88d4cba72174"},{"type":"PACKAGE","url":"https://github.com/getgrav/grav"},{"type":"WEB","url":"https://github.com/getgrav/grav/releases/tag/1.7.53"},{"type":"WEB","url":"https://github.com/getgrav/grav/releases/tag/2.0.0-rc.8"}],"affected":[{"package":{"name":"getgrav/grav","ecosystem":"Packagist","purl":"pkg:composer/getgrav/grav"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.0.0-beta.1"},{"fixed":"2.0.0-rc.8"}]}],"versions":["2.0.0-beta.1","2.0.0-beta.2","2.0.0-beta.3","2.0.0-beta.4","2.0.0-rc.1","2.0.0-rc.2","2.0.0-rc.3","2.0.0-rc.4","2.0.0-rc.5","2.0.0-rc.6","2.0.0-rc.7"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/08/GHSA-4x9g-vw65-vvf9/GHSA-4x9g-vw65-vvf9.json"}},{"package":{"name":"getgrav/grav","ecosystem":"Packagist","purl":"pkg:composer/getgrav/grav"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.7.53"}]}],"versions":["0.8.0","0.9.0","0.9.1","0.9.10","0.9.11","0.9.12","0.9.13","0.9.14","0.9.15","0.9.16","0.9.17","0.9.18","0.9.19","0.9.2","0.9.20","0.9.21","0.9.22","0.9.23","0.9.24","0.9.25","0.9.26","0.9.27","0.9.28","0.9.29","0.9.3","0.9.30","0.9.31","0.9.32","0.9.33","0.9.34","0.9.35","0.9.36","0.9.37","0.9.38","0.9.39","0.9.4","0.9.40","0.9.41","0.9.42","0.9.43","0.9.44","0.9.45","0.9.5","0.9.6","0.9.7","0.9.8","0.9.9","1.0.0","1.0.0-rc.1","1.0.0-rc.2","1.0.0-rc.3","1.0.0-rc.4","1.0.0-rc.5","1.0.0-rc.6","1.0.1","1.0.10","1.0.2","1.0.3","1.0.4","1.0.5","1.0.6","1.0.7","1.0.8","1.0.9","1.1.0","1.1.0-beta.1","1.1.0-beta.2","1.1.0-beta.3","1.1.0-beta.4","1.1.0-beta.5","1.1.0-rc.1","1.1.0-rc.2","1.1.0-rc.3","1.1.1","1.1.10","1.1.11","1.1.12","1.1.13","1.1.14","1.1.15","1.1.16","1.1.17","1.1.2","1.1.3","1.1.4","1.1.5","1.1.6","1.1.7","1.1.8","1.1.9","1.1.9-rc.1","1.1.9-rc.2","1.1.9-rc.3","1.2.0","1.2.0-rc.1","1.2.0-rc.2","1.2.0-rc.3","1.2.1","1.2.2","1.2.3","1.2.4","1.3.0","1.3.0-rc.1","1.3.0-rc.2","1.3.0-rc.3","1.3.0-rc.4","1.3.0-rc.5","1.3.1","1.3.10","1.3.2","1.3.3","1.3.4","1.3.5","1.3.6","1.3.7","1.3.8","1.3.9","1.4.0","1.4.0-beta.1","1.4.0-beta.2","1.4.0-beta.3","1.4.0-rc.1","1.4.0-rc.2","1.4.1","1.4.2","1.4.3","1.4.4","1.4.5","1.4.6","1.4.7","1.4.8","1.5.0","1.5.0-beta.1","1.5.0-beta.2","1.5.0-rc.1","1.5.1","1.5.10","1.5.2","1.5.3","1.5.4","1.5.5","1.5.6","1.5.7","1.5.8","1.5.9","1.6.0","1.6.0-beta.1","1.6.0-beta.2","1.6.0-beta.3","1.6.0-beta.4","1.6.0-beta.5","1.6.0-beta.6","1.6.0-beta.7","1.6.0-beta.8","1.6.0-rc.1","1.6.0-rc.2","1.6.0-rc.3","1.6.0-rc.4","1.6.1","1.6.10","1.6.11","1.6.12","1.6.13","1.6.14","1.6.15","1.6.16","1.6.17","1.6.18","1.6.19","1.6.2","1.6.20","1.6.21","1.6.22","1.6.23","1.6.24","1.6.25","1.6.26","1.6.27","1.6.28","1.6.29","1.6.3","1.6.30","1.6.31","1.6.4","1.6.5","1.6.6","1.6.7","1.6.8","1.6.9","1.7.0","1.7.0-beta.1","1.7.0-beta.10","1.7.0-beta.2","1.7.0-beta.3","1.7.0-beta.4","1.7.0-beta.5","1.7.0-beta.6","1.7.0-beta.7","1.7.0-beta.8","1.7.0-beta.9","1.7.0-rc.1","1.7.0-rc.10","1.7.0-rc.11","1.7.0-rc.12","1.7.0-rc.13","1.7.0-rc.14","1.7.0-rc.15","1.7.0-rc.16","1.7.0-rc.17","1.7.0-rc.18","1.7.0-rc.19","1.7.0-rc.2","1.7.0-rc.20","1.7.0-rc.3","1.7.0-rc.4","1.7.0-rc.5","1.7.0-rc.6","1.7.0-rc.7","1.7.0-rc.8","1.7.0-rc.9","1.7.1","1.7.10","1.7.12","1.7.13","1.7.14","1.7.15","1.7.16","1.7.17","1.7.18","1.7.19","1.7.20","1.7.21","1.7.22","1.7.23","1.7.24","1.7.25","1.7.26","1.7.26.1","1.7.27","1.7.27.1","1.7.28","1.7.29","1.7.29.1","1.7.3","1.7.30","1.7.31","1.7.32","1.7.33","1.7.34","1.7.35","1.7.36","1.7.37","1.7.37.1","1.7.38","1.7.39","1.7.39.1","1.7.39.2","1.7.39.3","1.7.39.4","1.7.4","1.7.40","1.7.41","1.7.41.1","1.7.41.2","1.7.42","1.7.42.1","1.7.42.2","1.7.42.3","1.7.43","1.7.44","1.7.45","1.7.46","1.7.47","1.7.48","1.7.49","1.7.49.1","1.7.49.2","1.7.49.3","1.7.49.4","1.7.49.5","1.7.5","1.7.51","1.7.52","1.7.6","1.7.7","1.7.8","1.7.9"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/08/GHSA-4x9g-vw65-vvf9/GHSA-4x9g-vw65-vvf9.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"}]}