{"id":"CVE-2021-21264","aliases":["GHSA-fcr8-6q7r-m4wg"],"url":"https://o3.security/vulnerability/CVE-2021-21264","summary":"Bypass of fix for CVE-2020-26231, Twig sandbox escape","details":"### Impact\nA bypass of CVE-2020-26231 (fixed in 1.0.470/471 and 1.1.1) was discovered that has the same impact as CVE-2020-26231 & CVE-2020-15247:\n\nAn authenticated backend user with the `cms.manage_pages`, `cms.manage_layouts`, or `cms.manage_partials` permissions who would **normally** not be permitted to provide PHP code to be executed by the CMS due to `cms.enableSafeMode` being enabled is able to write specific Twig code to escape the Twig sandbox and execute arbitrary PHP.\n\nThis is not a problem for anyone that trusts their users with those permissions to normally write & manage PHP within the CMS by not having `cms.enableSafeMode` enabled, but would be a problem for anyone relying on `cms.enableSafeMode` to ensure that users with those permissions in production do not have access to write & execute arbitrary PHP.\n\n### Patches\nIssue has been patched in Build 472 (v1.0.472) and v1.1.2.\n\n### Workarounds\nApply https://github.com/octobercms/october/commit/f63519ff1e8d375df30deba63156a2fc97aa9ee7 to your installation manually if unable to upgrade to Build 472 or v1.1.2.\n\n### References\nReported by [ka1n4t](https://github.com/ka1n4t)\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Email us at [hello@octobercms.com](mailto:hello@octobercms.com)\n\n### Threat assessment:\n<img width=\"1108\" alt=\"Screen Shot 2020-10-10 at 1 21 13 PM\" src=\"https://user-images.githubusercontent.com/7253840/95663316-7de28b80-0afb-11eb-999d-a6526cf78709.png\">","published":"2021-05-03T16:15:07.510Z","modified":"2026-09-22T08:11:24.735895Z","cvss":{"score":5.2,"severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:L"},"epss":{"score":0.00262,"percentile":0.1795,"asOf":"2026-08-11"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Packagist","name":"october/cms","fixedVersion":"1.0.472"},{"ecosystem":"Packagist","name":"october/cms","fixedVersion":"1.1.2"}],"fix":null,"references":[{"type":"FIX","url":"https://github.com/octobercms/october/security/advisories/GHSA-fcr8-6q7r-m4wg"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-21264"},{"type":"PACKAGE","url":"https://github.com/octobercms/october"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-22T08:11:24.735895Z"}}