Auth bypass in Wintercms Winter
CVE-2026-27591
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.9 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.008 (53.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 54th percentile — 53.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.008 · change: +0.003
Affected products
- Wintercms Winter — versions >= 1.2.0, < 1.2.12, >= 1.1.0, < 1.1.12, < 1.0.477
Weakness classification (CWE)
References
- github.com/wintercms/winter/security/advisories/GHSA-pgpf-m8m4-6cg6 (Patch, Vendor Advisory)
- wintercms.com/releases/v1.0.477 (Release Notes)
- wintercms.com/releases/v1.1.12 (Release Notes)
- wintercms.com/releases/v1.2.12 (Release Notes)
Frequently asked questions
- What is CVE-2026-27591?
- CVE-2026-27591 is a critical-severity vulnerability in Wintercms Winter, classified under Improper Access Control. CVSS score: 9.9/10. Published 2026-03-11.
- How severe is CVE-2026-27591?
- Critical severity. CVSS v3 base score is 9.9 out of 10.