CVE-2026-27591
Winter: Privilege escalation by authenticated backend users
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Winter: Privilege escalation by authenticated backend users
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.
- Record
CVE-2026-27591- CVSS 3.1
- 10.0 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - Weakness
- CWE-284, CWE-639, CWE-915
- Updated
- 2026-11-02
EUVDEUVD-2026-11406
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.
- Record
EUVD-2026-11406- CVSS 3.1
- 10.0 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-pgpf-m8m4-6cg6
Winter vulnerable to privilege escalation by authenticated backend users
Impact
Affected 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.
To actively exploit this security issue, an attacker would need access to the Backend with a user account with any level of access.
The 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).
Patches
Multiple fixes and defence in depth has been applied to prevent current and future privilege escalation attacks at the lowest level possible.
This 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.
Workarounds
If you cannot upgrade, you may apply the changes from the releases to your Winter CMS installation manually to resolve this issue.
- Record
GHSA-pgpf-m8m4-6cg6- CVSS 3.1
- 9.9 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - Weakness
- CWE-284, CWE-639, CWE-915
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2026-27591- CVSS 3.1
- 9.9 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - Weakness
- CWE-284, CWE-639, CWE-915
- Updated
- 2026-11-02
OSV
Winter: Privilege escalation by authenticated backend users
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.
- Record
CVE-2026-27591- CVSS 3.1
- 9.9 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - Weakness
- CWE-284, CWE-639, CWE-915
- Updated
- 2026-11-02
OSVGHSA-pgpf-m8m4-6cg6
Winter vulnerable to privilege escalation by authenticated backend users
Impact
Affected 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.
To actively exploit this security issue, an attacker would need access to the Backend with a user account with any level of access.
The 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).
Patches
Multiple fixes and defence in depth has been applied to prevent current and future privilege escalation attacks at the lowest level possible.
This 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.
Workarounds
If you cannot upgrade, you may apply the changes from the releases to your Winter CMS installation manually to resolve this issue.
- Record
GHSA-pgpf-m8m4-6cg6- CVSS 3.1
- 9.9 Critical
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - Weakness
- CWE-284, CWE-639, CWE-915
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
winter/wn-backend-modulePackagist |
1.2.0 up to 1.2.12 | 1.2.12 |
winter/wn-backend-modulePackagist |
1.1.0 up to 1.1.12 | 1.1.12 |
winter/wn-backend-modulePackagist |
before 1.0.477 | 1.0.477 |
winter/wn-backend-modulePackagist |
1.2.0 up to 1.2.12, plus listed versions v1.2.0v1.2.1v1.2.10v1.2.11v1.2.2 Show 7 moreShow lessv1.2.3v1.2.4v1.2.5v1.2.6v1.2.7v1.2.8v1.2.9 |
1.2.12 |
winter/wn-backend-modulePackagist |
1.1.0 up to 1.1.12, plus listed versions v1.1.10v1.1.11v1.1.2v1.1.3v1.1.4 Show 5 moreShow lessv1.1.5v1.1.6v1.1.7v1.1.8v1.1.9 |
1.1.12 |
winter/wn-backend-modulePackagist |
before 1.0.477, plus listed versions v1.0.473v1.0.474v1.0.475 |
1.0.477 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-27591 is a critical vulnerability (CVSS 10.0) in Wintercms Winter, published March 11, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.78%, the 56th percentile. Fixed in winter/wn-backend-module 1.2.12.
References
github.com/wintercms/winter/security/advisories/GHSA-pgpf-m8m4-6cg6
wintercms.com/releases/v1.0.477
nvd.nist.gov/vuln/detail/CVE-2026-27591