CVE-2026-40474: wger Privilege Escalation Vulnerability

CVE-2026-40474 Overview

CVE-2026-40474 is a vertical privilege escalation vulnerability in wger, a free, open-source workout and fitness manager application. The vulnerability exists in the GymConfigUpdateView class, which declares permission_required = 'config.change_gymconfig' but inherits from WgerFormMixin instead of WgerPermissionMixin. This inheritance error causes the permission check to never be enforced at runtime, allowing any authenticated user to modify the global gym configuration.

Critical Impact

Any authenticated user can modify installation-wide gym configuration settings, triggering bulk updates to user profile gym assignments and achieving vertical privilege escalation to installation-wide configuration control.

Affected Products

• wger Workout Manager versions 2.5 and below

Discovery Timeline

• 2026-04-17 - CVE-2026-40474 published to NVD
• 2026-04-20 - Last updated in NVD database

Technical Details for CVE-2026-40474

Vulnerability Analysis

This vulnerability is classified under CWE-284 (Improper Access Control). The core issue stems from an incorrect class inheritance pattern in the Django-based wger application. The GymConfigUpdateView view class properly declares the required permission string but fails to enforce it because it inherits from the wrong mixin class.

In Django applications, permission enforcement typically occurs through mixin classes that check user permissions before processing requests. The WgerPermissionMixin is designed to perform this enforcement, while WgerFormMixin provides form handling functionality without permission verification. By inheriting from WgerFormMixin instead of WgerPermissionMixin, the permission declaration becomes purely decorative with no runtime effect.

The GymConfig model is implemented as an ownerless singleton, meaning there is only one configuration object for the entire installation that is not associated with any specific owner. When this configuration is modified through the unprotected view, the save() method triggers side effects that bulk-update user profile gym assignments across the entire installation.

Root Cause

The root cause is an incorrect mixin inheritance pattern in the GymConfigUpdateView class. While the view correctly specifies permission_required = 'config.change_gymconfig', this permission is never evaluated because the WgerFormMixin parent class does not implement permission checking logic. The WgerPermissionMixin class, which would enforce the permission requirement, was not included in the class inheritance chain.

Attack Vector

An attacker with any valid authenticated session in the wger application can exploit this vulnerability through network-based requests. The attack requires no special privileges beyond basic authentication, making it accessible to any registered user.

The exploitation flow involves:

1. Authenticating to the wger application with any valid user account
2. Accessing the GymConfigUpdateView endpoint directly
3. Submitting a modified gym configuration payload
4. The configuration changes are applied without permission verification
5. The save() method executes, potentially bulk-updating all user profile gym assignments

This attack enables vertical privilege escalation, allowing regular users to perform administrative actions that should be restricted to users with the config.change_gymconfig permission.

Detection Methods for CVE-2026-40474

Indicators of Compromise

• Unexpected modifications to gym configuration settings by non-administrative users
• Audit logs showing GymConfig model changes from accounts without config.change_gymconfig permission
• Bulk changes to user profile gym assignments without corresponding administrative actions
• HTTP requests to the gym configuration update endpoint from regular user sessions

Detection Strategies

• Monitor application logs for POST requests to the gym configuration update endpoint
• Implement audit logging on GymConfig model changes to track the requesting user
• Review Django middleware logs for permission bypass indicators
• Alert on configuration changes originating from user accounts without administrative roles

Monitoring Recommendations

• Enable detailed access logging for configuration-related views in the wger application
• Implement real-time alerting for any modifications to the GymConfig singleton object
• Deploy web application firewall rules to monitor requests to sensitive configuration endpoints
• Establish baseline normal behavior for configuration changes to identify anomalies

How to Mitigate CVE-2026-40474

Immediate Actions Required

• Upgrade wger to version 2.5 or later, which contains the fix for this vulnerability
• Review recent GymConfig changes and user gym assignments for unauthorized modifications
• Audit user accounts for suspicious activity related to configuration access
• Consider implementing additional access controls at the web server level while awaiting the upgrade

Patch Information

The vulnerability has been fixed in wger version 2.5. The fix involves correcting the class inheritance to use WgerPermissionMixin, ensuring the permission_required declaration is properly enforced at runtime.

For detailed patch information, refer to the GitHub commit that addresses this issue. The official release is available at the wger version 2.5 release page. Additional details can be found in the GitHub Security Advisory GHSA-xppv-4jrx-qf8m.

Workarounds

• Restrict access to the gym configuration update endpoint at the web server or reverse proxy level
• Implement additional Django middleware to enforce permission checks on sensitive views
• Temporarily disable the gym configuration update functionality until the patch can be applied
• Use network segmentation to limit access to the wger administrative interface

# Example nginx configuration to restrict access to gym config endpoint
location /gym/config/ {
    # Restrict to specific admin IP addresses
    allow 192.168.1.0/24;
    deny all;
    proxy_pass http://wger_backend;
}