{"id":"CVE-2023-37897","aliases":["EUVD-2023-2010","GHSA-9436-3gmp-4f53"],"status":"published","title":"Server-side Template Injection (SSTI) in grav","description":"Grav is a file-based Web-platform built in PHP. Grav is subject to a server side template injection (SSTI) vulnerability. The fix for another SSTI vulnerability using `|map`, `|filter` and `|reduce` twigs implemented in the commit `71bbed1` introduces bypass of the denylist due to incorrect return value from `isDangerousFunction()`, which allows to execute the payload prepending double backslash (`\\\\`). The `isDangerousFunction()` check in version 1.7.42 and onwards retuns `false` value instead of `true` when the `\\` symbol is found in the `$name`. This vulnerability can be exploited if the attacker has access to: 1. an Administrator account, or 2. a non-administrator, user account that has Admin panel access and Create/Update page permissions. A fix for this vulnerability has been introduced in commit `b4c6210` and is included in release version `1.7.42.2`. Users are advised to upgrade. There are no known workarounds for this vulnerability.","severity":{"version":"3.1","score":7.2,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.02809,"percentile":0.86626,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-393","CWE-74"],"published":"2023-07-18T20:22:13Z","modified":"2026-10-28T02:30:52Z","fixes":[{"ecosystem":"Packagist","package":"getgrav/grav","fixed_in":["1.7.42.2"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"Packagist","package":"getgrav/grav","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"1.7.42.1"},{"fixed":"1.7.42.2"}]}]},{"source":"osv","ecosystem":"Packagist","package":"getgrav/grav","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.7.42.2"}]}],"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","1.7.5","1.7.6","1.7.7","1.7.8","1.7.9"]}],"products":[{"vendor":"getgrav","product":"grav"}],"references":[{"url":"https://github.com/getgrav/grav/security/advisories/GHSA-9436-3gmp-4f53","tags":["x_refsource_CONFIRM","x_transferred","Exploit","Mitigation","Vendor Advisory","advisory","web"]},{"url":"https://github.com/getgrav/grav/commit/71bbed12f950de8335006d7f91112263d8504f1b","tags":["x_refsource_MISC","x_transferred","Product","fix","web"]},{"url":"https://github.com/getgrav/grav/commit/b4c62101a43051fc7f5349c7d0a5b6085375c1d7","tags":["x_refsource_MISC","x_transferred","Patch","fix","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2023-37897","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-9436-3gmp-4f53"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/37xxx/CVE-2023-37897.json","tags":["advisory"]},{"url":"https://github.com/getgrav/grav","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2023-37897","title":"Server-side Template Injection (SSTI) in grav","description":"Grav is a file-based Web-platform built in PHP. Grav is subject to a server side template injection (SSTI) vulnerability. The fix for another SSTI vulnerability using `|map`, `|filter` and `|reduce` twigs implemented in the commit `71bbed1` introduces bypass of the denylist due to incorrect return value from `isDangerousFunction()`, which allows to execute the payload prepending double backslash (`\\\\`). The `isDangerousFunction()` check in version 1.7.42 and onwards retuns `false` value instead of `true` when the `\\` symbol is found in the `$name`. This vulnerability can be exploited if the attacker has access to: 1. an Administrator account, or 2. a non-administrator, user account that has Admin panel access and Create/Update page permissions. A fix for this vulnerability has been introduced in commit `b4c6210` and is included in release version `1.7.42.2`. Users are advised to upgrade. There are no known workarounds for this vulnerability.\n\n","status":"published","published":"2023-07-18T20:22:13.008Z","modified":"2024-10-18T17:19:07.91Z","cvss":[{"version":"3.1","score":7.2,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-74","CWE-393"],"updated_at":"2026-11-02T14:35:16.454633Z"}],"euvd":[{"id":"EUVD-2023-2010","description":"Grav is a file-based Web-platform built in PHP. Grav is subject to a server side template injection (SSTI) vulnerability. The fix for another SSTI vulnerability using `|map`, `|filter` and `|reduce` twigs implemented in the commit `71bbed1` introduces bypass of the denylist due to incorrect return value from `isDangerousFunction()`, which allows to execute the payload prepending double backslash (`\\\\`). The `isDangerousFunction()` check in version 1.7.42 and onwards retuns `false` value instead of `true` when the `\\` symbol is found in the `$name`. This vulnerability can be exploited if the attacker has access to: 1. an Administrator account, or 2. a non-administrator, user account that has Admin panel access and Create/Update page permissions. A fix for this vulnerability has been introduced in commit `b4c6210` and is included in release version `1.7.42.2`. Users are advised to upgrade. There are no known workarounds for this vulnerability.\n\n","status":"published","published":"2023-07-18T20:22:13Z","modified":"2024-10-18T17:19:07Z","cvss":[{"version":"3.1","score":7.2,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-03T00:27:32.691525Z"}],"ghsa":[{"id":"GHSA-9436-3gmp-4f53","title":"grav Server-side Template Injection (SSTI) mitigation bypass","description":"### Summary\nThe fix for SSTI using `|map`, `|filter` and `|reduce` twigs implemented in the commit [71bbed1](https://github.com/getgrav/grav/commit/71bbed12f950de8335006d7f91112263d8504f1b) introduces bypass of the denylist due to incorrect return value from `isDangerousFunction()`, which allows to execute the payload prepending double backslash (`\\\\`) \n\n### Details\nThe `isDangerousFunction()` check in version 1.7.42 and onwards retuns `false` value instead of `true` when the `\\` symbol is found in the `$name`.\n\n```php\n...\n        if (strpos($name, \"\\\\\") !== false) {\n            return false;\n        }\n\n        if (in_array($name, $commandExecutionFunctions)) {\n            return true;\n        }\n...\n```\nBased on the code where the function is used, it is expected that any dangerous condition would return `true`\n```php\n    /**\n     * @param Environment $env\n     * @param array $array\n     * @param callable|string $arrow\n     * @return array|CallbackFilterIterator\n     * @throws RuntimeError\n     */\n    function mapFunc(Environment $env, $array, $arrow)\n    {\n        if (!$arrow instanceof \\Closure \u0026\u0026 !is_string($arrow) || Utils::isDangerousFunction($arrow)) {\n            throw new RuntimeError('Twig |map(\"' . $arrow . '\") is not allowed.');\n\t}\n```\nwhen `|map('\\system')` is used in the malicious payload, the single backslash is dropped prior to reaching `strpos($name, '\\\\')` check, thus `$name` variable already has no backslash, and the command is blacklisted because it reaches the  `if (in_array($name, $commandExecutionFunctions)) {` validation step. \n\nHowever if `|map('\\\\system')` is used (i.e. double backslash), then the `strpos($name, \"\\\\\") !== false` takes effect, and `isDangerousFunction()` returns `false` , in which case the `RuntimeError` is not generated, and blacklist is bypassed leading to code execution.\n\n### Exploit Conditions\nThis vulnerability can be exploited if the attacker has access to:\n\n1. an Administrator account, or\n2. a non-administrator, user account that has Admin panel access and Create/Update page permissions\n\n### Steps to reproduce\n\n1. Log in to Grav Admin using an administrator account.\n2. Navigate to `Accounts \u003e Add`, and ensure that the following permissions are assigned when creating a new low-privileged user: \n    - Login to Admin - Allowed\n    - Page Update - Allowed\n3. Log out of Grav Admin\n4. Login using the account created in step 2.\n5. Choose `Pages -\u003e Home`\n6. Click the `Advanced` tab and select the checkbox beside `Twig` to ensure that Twig processing is enabled for the modified webpage.\n7. Under the `Content` tab, insert the following payload within the editor:\n```{{ ['id'] | map('\\\\system') | join() }}```\n8. Click the `Preview` button. Observe that the output of the id shell command is returned in the preview.\n\n### Mitigation\n\n```diff\ndiff --git a/system/src/Grav/Common/Utils.php b/system/src/Grav/Common/Utils.php\nindex 2f121bbe3..7b267cd0f 100644\n--- a/system/src/Grav/Common/Utils.php\n+++ b/system/src/Grav/Common/Utils.php\n@@ -2069,7 +2069,7 @@ abstract class Utils\n         }\n \n         if (strpos($name, \"\\\\\") !== false) {\n-            return false;\n+            return true;\n         }\n \n         if (in_array($name, $commandExecutionFunctions)) {\n                                                                         \n```\n\n","status":"published","published":"2023-07-19T22:11:07Z","modified":"2023-11-10T05:03:41Z","cvss":[{"version":"3.1","score":7.2,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-74","CWE-393"],"updated_at":"2026-11-02T14:37:19.438667Z"}],"nvd":[{"id":"CVE-2023-37897","description":"Grav is a file-based Web-platform built in PHP. Grav is subject to a server side template injection (SSTI) vulnerability. The fix for another SSTI vulnerability using `|map`, `|filter` and `|reduce` twigs implemented in the commit `71bbed1` introduces bypass of the denylist due to incorrect return value from `isDangerousFunction()`, which allows to execute the payload prepending double backslash (`\\\\`). The `isDangerousFunction()` check in version 1.7.42 and onwards retuns `false` value instead of `true` when the `\\` symbol is found in the `$name`. This vulnerability can be exploited if the attacker has access to: 1. an Administrator account, or 2. a non-administrator, user account that has Admin panel access and Create/Update page permissions. A fix for this vulnerability has been introduced in commit `b4c6210` and is included in release version `1.7.42.2`. Users are advised to upgrade. There are no known workarounds for this vulnerability.\n\n","status":"published","published":"2023-07-18T21:15:15.663Z","modified":"2026-06-17T06:08:51.333Z","cvss":[{"version":"3.1","score":7.2,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"secondary"},{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"primary"}],"cwes":["CWE-74","CWE-393"],"updated_at":"2026-11-02T14:08:17.044696Z"}],"osv":[{"id":"CVE-2023-37897","title":"Server-side Template Injection (SSTI) in grav","description":"Grav is a file-based Web-platform built in PHP. Grav is subject to a server side template injection (SSTI) vulnerability. The fix for another SSTI vulnerability using `|map`, `|filter` and `|reduce` twigs implemented in the commit `71bbed1` introduces bypass of the denylist due to incorrect return value from `isDangerousFunction()`, which allows to execute the payload prepending double backslash (`\\\\`). The `isDangerousFunction()` check in version 1.7.42 and onwards retuns `false` value instead of `true` when the `\\` symbol is found in the `$name`. This vulnerability can be exploited if the attacker has access to: 1. an Administrator account, or 2. a non-administrator, user account that has Admin panel access and Create/Update page permissions. A fix for this vulnerability has been introduced in commit `b4c6210` and is included in release version `1.7.42.2`. Users are advised to upgrade. There are no known workarounds for this vulnerability.\n\n","status":"published","published":"2023-07-18T20:22:13.008Z","modified":"2026-10-28T02:30:52.833142449Z","cvss":[{"version":"3.1","score":7.2,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-393","CWE-74"],"updated_at":"2026-11-02T15:44:32.922049Z"},{"id":"GHSA-9436-3gmp-4f53","title":"grav Server-side Template Injection (SSTI) mitigation bypass","description":"### Summary\nThe fix for SSTI using `|map`, `|filter` and `|reduce` twigs implemented in the commit [71bbed1](https://github.com/getgrav/grav/commit/71bbed12f950de8335006d7f91112263d8504f1b) introduces bypass of the denylist due to incorrect return value from `isDangerousFunction()`, which allows to execute the payload prepending double backslash (`\\\\`) \n\n### Details\nThe `isDangerousFunction()` check in version 1.7.42 and onwards retuns `false` value instead of `true` when the `\\` symbol is found in the `$name`.\n\n```php\n...\n        if (strpos($name, \"\\\\\") !== false) {\n            return false;\n        }\n\n        if (in_array($name, $commandExecutionFunctions)) {\n            return true;\n        }\n...\n```\nBased on the code where the function is used, it is expected that any dangerous condition would return `true`\n```php\n    /**\n     * @param Environment $env\n     * @param array $array\n     * @param callable|string $arrow\n     * @return array|CallbackFilterIterator\n     * @throws RuntimeError\n     */\n    function mapFunc(Environment $env, $array, $arrow)\n    {\n        if (!$arrow instanceof \\Closure \u0026\u0026 !is_string($arrow) || Utils::isDangerousFunction($arrow)) {\n            throw new RuntimeError('Twig |map(\"' . $arrow . '\") is not allowed.');\n\t}\n```\nwhen `|map('\\system')` is used in the malicious payload, the single backslash is dropped prior to reaching `strpos($name, '\\\\')` check, thus `$name` variable already has no backslash, and the command is blacklisted because it reaches the  `if (in_array($name, $commandExecutionFunctions)) {` validation step. \n\nHowever if `|map('\\\\system')` is used (i.e. double backslash), then the `strpos($name, \"\\\\\") !== false` takes effect, and `isDangerousFunction()` returns `false` , in which case the `RuntimeError` is not generated, and blacklist is bypassed leading to code execution.\n\n### Exploit Conditions\nThis vulnerability can be exploited if the attacker has access to:\n\n1. an Administrator account, or\n2. a non-administrator, user account that has Admin panel access and Create/Update page permissions\n\n### Steps to reproduce\n\n1. Log in to Grav Admin using an administrator account.\n2. Navigate to `Accounts \u003e Add`, and ensure that the following permissions are assigned when creating a new low-privileged user: \n    - Login to Admin - Allowed\n    - Page Update - Allowed\n3. Log out of Grav Admin\n4. Login using the account created in step 2.\n5. Choose `Pages -\u003e Home`\n6. Click the `Advanced` tab and select the checkbox beside `Twig` to ensure that Twig processing is enabled for the modified webpage.\n7. Under the `Content` tab, insert the following payload within the editor:\n```{{ ['id'] | map('\\\\system') | join() }}```\n8. Click the `Preview` button. Observe that the output of the id shell command is returned in the preview.\n\n### Mitigation\n\n```diff\ndiff --git a/system/src/Grav/Common/Utils.php b/system/src/Grav/Common/Utils.php\nindex 2f121bbe3..7b267cd0f 100644\n--- a/system/src/Grav/Common/Utils.php\n+++ b/system/src/Grav/Common/Utils.php\n@@ -2069,7 +2069,7 @@ abstract class Utils\n         }\n \n         if (strpos($name, \"\\\\\") !== false) {\n-            return false;\n+            return true;\n         }\n \n         if (in_array($name, $commandExecutionFunctions)) {\n                                                                         \n```\n\n","status":"published","published":"2023-07-19T22:11:07Z","modified":"2024-02-16T08:16:43.971294Z","cvss":[{"version":"3.1","score":7.2,"vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-393","CWE-74"],"updated_at":"2026-11-02T15:46:43.123867Z"}]}}