{"id":"CVE-2026-27591","aliases":["GHSA-pgpf-m8m4-6cg6"],"url":"https://o3.security/vulnerability/CVE-2026-27591","summary":"Winter: Privilege escalation by authenticated backend users","details":"## Impact\nAffected versions of Winter CMS allowed authenticated backend users to escalate their accounts level of access to the system by modifying the roles / permissions assigned to their account through specially crafted requests to the backend while logged in.\n\nTo actively exploit this security issue, an attacker would need access to the Backend with a user account with any level of access.\n\nThe Winter CMS maintainers strongly recommend that all Winter CMS sites that have any reliance on the roles & permissions system to update immediately. Security fixes have been backported to all major versions of Winter (1.0, 1.1, and 1.2).\n\n## Patches\nMultiple fixes and defence in depth has been applied to prevent current and future privilege escalation attacks at the lowest level possible.\n\nThis security issue has been fixed as of https://wintercms.com/releases/v1.0.477, https://wintercms.com/releases/v1.1.12, https://wintercms.com/releases/v1.2.12.\n\n## Workarounds\nIf you cannot upgrade, you may apply the changes from the releases to your Winter CMS installation manually to resolve this issue.","published":"2026-03-11T21:25:35.289Z","modified":"2026-08-12T03:51:48.513949712Z","cvss":{"score":9.9,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H"},"epss":{"score":0.00486,"percentile":0.39208,"asOf":"2026-08-05"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Packagist","name":"winter/wn-backend-module","fixedVersion":"1.2.12"},{"ecosystem":"Packagist","name":"winter/wn-backend-module","fixedVersion":"1.1.12"},{"ecosystem":"Packagist","name":"winter/wn-backend-module","fixedVersion":"1.0.477"}],"fix":null,"references":[{"type":"WEB","url":"https://wintercms.com/releases/v1.0.477"},{"type":"WEB","url":"https://wintercms.com/releases/v1.1.12"},{"type":"WEB","url":"https://wintercms.com/releases/v1.2.12"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27591.json"},{"type":"ADVISORY","url":"https://github.com/wintercms/winter/security/advisories/GHSA-pgpf-m8m4-6cg6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27591"},{"type":"PACKAGE","url":"https://github.com/wintercms/winter"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:48.513949712Z"}}