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EUVD-2026-359564

fkie_cve-2026-35445

Winter CMS is a content management system built on the Laravel PHP framework. In versions prior to 1.2.13, the backend did not validate the handler name submitted through the form postback _handler POST field, allowing an authenticated backend user to invoke arbitrary controller methods, including protected, private, and action-prefixed ones. While AJAX requests validate that handler names match the on[A-Z][\w+]* pattern, the postback path passed the submitted _handler value straight to the handler dispatcher with no such check, so any controller that exposes a public action or conditionally relaxes its $requiredPermissions check could be reached, bypassing the roles and permissions system. The built-in Users controller was affected because it set $requiredPermissions to null for the myaccount action, letting any authenticated backend user invoke user-management methods such as update_onDelete and update_onManualPasswordReset without holding the backend.manage_users permission. This issue is fixed in version 1.2.13.

GHSA-j5jq-cr68-v2xx — Winter: Authenticated backend users can bypass Users controller permission checks

Affected: Packagist: winter/wn-backend-module

### Impact

Affected versions of Winter CMS did not validate the handler name submitted through the form postback mechanism (`_handler` POST field) in the same way as AJAX requests (`X_WINTER_REQUEST_HANDLER` header). The AJAX path validates that handler names match the `on[A-Z][\w+]*` pattern, but the postback path passed the handler name directly to the handler dispatcher with no validation.

This allowed an authenticated backend user to call any method on a controller — including action-prefixed, protected, and private methods — by submitting a crafted POST request with a `_handler` field, as long as the controller either:

- Contains a publicly available action via the `$publicActions` property, or - Degrades or removes the `$requiredPermissions` check in its constructor based on a condition

The backend's own Users controller was affected by the second scenario: it set `$requiredPermissions` to `null` for the `myaccount` action, allowing any authenticated backend user to access the controller without the `backend.manage_users` permission. Combined with the postback bypass, this allowed calling controller methods such as `update_onDelete`, `update_onRestore`, `update_onUnsuspendUser`, and `update_onManualPasswordReset` with attacker-controlled parameters.

Note that CSRF tokens are still verified on all POST requests, so the attacker must be logged into the backend with a valid session.

To actively exploit this security issue, an attacker would need access to the Backen…