Unrated

Permission Bypass in Winter CMS Users Controller via Crafted _handler

IdentifiersCVE-2026-35445CWE-863

CVE-2026-35445 is an authorization bypass vulnerability in the Winter CMS backend module affecting the Users controller. An authenticated backend user can supply a crafted _handler value in a POST request to bypass intended permission checks and trigger unauthorized controller methods. The issue stems from insufficient validation of postback handler names before they are passed to the AJAX handler dispatch mechanism, allowing invocation of methods that should not be reachable by the requesting user. As described, this can expose protected, private, or action-prefixed controller methods, including sensitive user-management functionality such as delete, restore, unsuspend, and manual password reset. The flaw is compounded by logic in the Users controller related to the myaccount action that weakens required permission enforcement.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows an authenticated backend user with otherwise limited backend access to perform unauthorized administrative actions within the Users controller. This can result in modification of user records, account state changes, password resets, deletion or restoration of accounts, and other unauthorized user-management operations. The vulnerability therefore compromises authorization boundaries inside the administrative backend and can lead to privilege abuse and integrity impact across managed user accounts.

Mitigation

If you can’t patch tonight, do this now.

If an immediate upgrade is not possible, implement strict server-side validation of the _handler POST parameter so that only expected AJAX handler names matching the intended on... handler pattern are accepted before dispatch. Additionally, remove the Users controller logic that nullifies required permissions for the myaccount action. Restrict backend access to only trusted users until patched, and review backend role assignments for unnecessary access.

Remediation

Patch, then assume compromise.

Upgrade the Winter CMS backend module to a fixed release. Version 1.2.13 or later is identified as containing the fix. The remediation includes consistent validation of postback handler names, relocation of My Account functionality to a dedicated controller, and additional defense-in-depth protections at the model layer. Fixes were also backported to the 1.0, 1.1, and 1.2 major branches.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

ACTIVITY FEED

Recent activity

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0 SOURCESView more in app

No public activity observed for this vulnerability.

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Exposure mapping

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Threat actor evidence

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Associated malware

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Detection signatures

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Vendor-by-vendor mapping

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Social activity