CVE-2026-32639 in Winter
Summary
by MITRE • 08/26/2026
Winter CMS is a content management system built on the Laravel PHP framework. In versions up to and including 1.2.12, the CMS section's Theme Editor AJAX handlers did not enforce per-template-type permission checks, allowing a backend user with any single CMS permission to act on template types outside their authorized scope. The CMS controller gated access to the section as a whole using OR-logic across its five permissions, but individual handlers such as onSave(), onDelete(), and onDeleteTemplates() did not verify that the user held the specific permission for the requested template type, so a user with only cms.manage_pages could craft AJAX requests to delete layouts, modify partials, or read content files. Separately, the AssetList widget was registered for any user who passed the controller gate regardless of the cms.manage_assets permission, and its onUpload() handler omitted the theme-validation call present on the other mutating handlers, permitting unauthorized file uploads into the active theme's asset directory. Exploitation requires an authenticated backend account holding at least one of the CMS Theme Editor permissions. This issue is fixed in version 1.2.13.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 08/26/2026
Winter CMS versions up to and including 1.2.12 contain a critical authorization bypass vulnerability within its theme editor functionality, stemming from inconsistent enforcement of role-based access control policies across different AJAX handlers. The system relies on the Laravel PHP framework for its backend operations, where security is typically managed through controller-level gates that evaluate user permissions using logical OR conditions. This design allows any backend user possessing at least one CMS-related permission to enter the theme editor section as a whole. However, this coarse-grained access control fails to translate into fine-grained authorization checks within individual action handlers such as onSave, onDelete, and onDeleteTemplates. Consequently, an authenticated attacker with limited privileges, such as only cms.manage_pages, can exploit these gaps to perform actions reserved for higher-privileged roles, including deleting layouts, modifying partials, or reading sensitive content files that should be restricted by template type permissions.
The technical flaw is rooted in the absence of specific permission verification within the AJAX handlers themselves. While the controller gate ensures entry into the section based on a broad set of credentials, it does not validate whether the user holds the specific authorization required for the particular resource being manipulated. This discrepancy allows an attacker to craft malicious AJAX requests that bypass intended restrictions, effectively elevating their privileges within the context of theme management. The vulnerability aligns with CWE-269, which describes Improper Privilege Management, as well as CWE-862, Missing Authorization, because the application fails to enforce proper access controls on specific resources despite having authentication in place. Furthermore, this behavior reflects ATT&CK technique T1078, Valid Accounts, where an attacker leverages legitimate credentials with insufficient privileges to perform unauthorized actions due to flawed implementation logic rather than credential theft.
A secondary but equally severe vulnerability exists within the AssetList widget and its associated onUpload handler. This component is registered for any user who passes the initial controller gate, regardless of whether they possess the specific cms.manage_assets permission required for asset management operations. More critically, the onUpload handler omits a theme-validation call that is present in other mutating handlers. This omission allows an authenticated attacker to upload arbitrary files directly into the active theme's asset directory without proper validation or authorization checks. This flaw facilitates CWE-434, Unrestricted Upload of File with Dangerous Type, and can lead to remote code execution if the uploaded file contains executable content that is subsequently served by the web server. The combination of these two vulnerabilities creates a significant risk profile where an attacker with minimal initial access can achieve substantial control over the CMS theme structure and potentially execute arbitrary code on the underlying system.
The operational impact of these vulnerabilities is severe, as they compromise the integrity and confidentiality of Winter CMS installations that have not yet applied the security patch. Attackers can deface websites by modifying themes, steal sensitive data embedded in content files or assets, and potentially gain full server control through malicious file uploads. This undermines the trust model of multi-user environments where different team members are assigned specific roles to limit their operational scope. The lack of granular permission checks means that even users intended to have read-only or limited editing access can perform destructive administrative actions, leading to potential service disruption and data loss for organizations relying on Winter CMS for their web presence.
Mitigation requires immediate action by upgrading the Winter CMS installation to version 1.2.13 or later, which addresses these authorization bypasses by implementing strict per-template-type permission checks in all relevant AJAX handlers and enforcing theme validation during asset uploads. Administrators should also audit existing user roles to ensure that permissions are assigned according to the principle of least privilege, minimizing the blast radius if a vulnerability were to be discovered in future updates. Additionally, web application firewalls can be configured to monitor for unusual patterns of AJAX requests targeting theme-related endpoints from users with low-level privileges, providing an additional layer of defense while patching is implemented. Regular security audits and penetration testing focused on role-based access control logic are recommended to identify similar implementation flaws before they can be exploited in production environments.