PHP
CVE-2026-27591
CRITICAL
GHSA-pgpf-m8m4-6cg6
Severity by source
AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Lifecycle Timeline
3DescriptionGitHub Advisory
Winter is a free, open-source content management system (CMS) based on the Laravel PHP framework. Prior to 1.0.477, 1.1.12, and 1.2.12, 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. To actively exploit this security issue, an attacker would need access to the Backend with a user account with any level of access. This vulnerability is fixed in 1.0.477, 1.1.12, and 1.2.12.
AnalysisAI
Access control bypass in Winter CMS before 1.0.477/1.1.12/1.2.12. CVSS 9.9.
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Valid authenticated Winter CMS backend user account with any privilege level. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | CVSS 9.9. Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Access CMS functions without authorization. |
| Remediation | Update. Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Identify all systems running Winter CMS and assess exposure; isolate critical instances if possible and enable enhanced monitoring. …
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