Summary
Winter: Broken access control in Cms\Controllers\Index allows cross-template actions and unauthorized asset uploads
Workarounds
If users cannot upgrade, they may apply the following changes to their Winter CMS installation manually to resolve this issue:
- In
modules/cms/controllers/Index.php, wrap each widget registration in the constructor with the correspondinghasAccess()check, and add avalidateRequestType()call to theindex_onOpenTemplate(),onSave(),onCreateTemplate(),onDeleteTemplates(),onDelete(),onCommit(), andonReset()handlers that verifies the user holds the permission for the requested template type. - In
modules/cms/widgets/AssetList.php, add a$this->validateRequestTheme()call at the top of theonUpload()method.
Impact
Affected versions of Winter CMS did not enforce per-template-type permission checks in the CMS section's AJAX handlers. The CMS controller (Cms\Controllers\Index) used OR-logic across its five permissions (cms.manage_pages, cms.manage_partials, cms.manage_layouts, cms.manage_content, cms.manage_assets) to control access to the section as a whole, but individual handlers such as onSave(), onDelete(), and onDeleteTemplates() did not verify that the authenticated user holds the specific permission corresponding to the requested template type.
This allowed a backend user with any single Theme Editor permission (e.g. cms.manage_pages) to craft AJAX requests targeting template types outside their authorized scope, for example, deleting layouts, modifying partials, or reading content files.
In addition, the AssetList widget was registered for all users who passed the controller gate regardless of whether they held the cms.manage_assets permission, and its onUpload() handler was missing the validateRequestTheme() call that is present on all other mutating handlers in the same widget. This allowed unauthorized file uploads into the active theme's asset directory.
To actively exploit this security issue, an attacker would need access to the Backend with a user account with any of the following permissions:
cms.manage_pagescms.manage_partialscms.manage_layoutscms.manage_contentcms.manage_assets
The Winter CMS maintainers strongly recommend that all Winter CMS sites that rely on granular CMS permission assignments (specifically users with only access to cms.manage_content to only be able to edit content files through the Theme Editor) to update immediately.
CVE-2026-32639 has a CVSS score of 6.8 (Medium). The vector is network-reachable, high privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.2.13); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Per-template-type permission checks are now enforced on all Theme Editor AJAX handlers, the AssetList widget is only registered for users with the cms.manage_assets permission, and onUpload() now includes theme validation consistent with the other mutating handlers.
This security issue has been fixed as of v1.2.13.
Frequently Asked Questions
- What is CVE-2026-32639? CVE-2026-32639 is a medium-severity security vulnerability in winter/wn-cms-module (composer), affecting versions <= 1.2.12. It is fixed in 1.2.13.
- How severe is CVE-2026-32639? CVE-2026-32639 has a CVSS score of 6.8 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of winter/wn-cms-module are affected by CVE-2026-32639? winter/wn-cms-module (composer) versions <= 1.2.12 is affected.
- Is there a fix for CVE-2026-32639? Yes. CVE-2026-32639 is fixed in 1.2.13. Upgrade to this version or later.
- Is CVE-2026-32639 exploitable, and should I be worried? Whether CVE-2026-32639 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-32639 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-32639? Upgrade
winter/wn-cms-moduleto 1.2.13 or later.