CVE-2016-20053: Redaxo CMS 5.2 CSRF Vulnerability

CVE-2016-20053 Overview

Redaxo CMS 5.2 contains a Cross-Site Request Forgery (CSRF) vulnerability that allows unauthenticated attackers to create administrative user accounts by tricking authenticated administrators into visiting malicious pages. This vulnerability exists in the users endpoint, where attackers can craft HTML forms with hidden fields containing admin credentials and account parameters to add new administrator accounts without user consent.

Critical Impact

Successful exploitation enables attackers to gain full administrative access to the CMS by creating rogue admin accounts, potentially leading to complete system compromise.

Affected Products

• Redaxo CMS version 5.2

Discovery Timeline

• 2026-04-04 - CVE-2016-20053 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2016-20053

Vulnerability Analysis

This Cross-Site Request Forgery (CSRF) vulnerability in Redaxo CMS 5.2 affects the users endpoint responsible for account management. The application fails to implement proper anti-CSRF token validation when processing requests to create new user accounts. This architectural weakness allows attackers to construct malicious web pages that automatically submit forged requests to the vulnerable endpoint when visited by an authenticated administrator.

The attack exploits the trust relationship between the CMS and authenticated admin sessions. When an administrator with an active session visits a malicious page controlled by the attacker, their browser automatically includes session cookies with the forged request. The CMS cannot distinguish between legitimate administrative actions and those triggered by the attacker's crafted form.

Root Cause

The root cause of this vulnerability is the absence of CSRF protection mechanisms on the user creation endpoint. The application does not require or validate anti-CSRF tokens (also known as synchronizer tokens or nonces) when processing POST requests to the /users endpoint. Without these tokens, the server cannot verify that requests originate from legitimate application forms rather than malicious external sources.

Attack Vector

The attack is network-based and requires social engineering to lure an authenticated administrator to a malicious website. The attacker creates an HTML page containing a hidden form that targets the Redaxo CMS users endpoint. This form includes all necessary parameters to create a new administrative account with attacker-controlled credentials. When the administrator visits this page, JavaScript automatically submits the form, or the attacker may use CSS tricks to disguise a submit button. The victim's browser sends the request with their valid session cookies, and the CMS processes it as a legitimate administrative action.

The attack requires no authentication from the attacker's perspective—they simply need to host a malicious page and convince an admin to visit it. Common delivery methods include phishing emails, compromised websites, or social media links. Technical details of the exploitation technique can be found in the Exploit-DB #40708 entry.

Detection Methods for CVE-2016-20053

Indicators of Compromise

• Unexpected new administrator accounts appearing in the Redaxo CMS user management panel
• User creation events in CMS logs without corresponding legitimate administrative actions
• Authentication logs showing admin activity from unusual IP addresses or at unusual times
• Web server access logs showing POST requests to the users endpoint with external Referer headers

Detection Strategies

• Monitor web application logs for user creation events and correlate with administrator activity patterns
• Implement web application firewall (WAF) rules to detect and block requests with suspicious Referer headers
• Review CMS audit logs regularly for unauthorized account modifications
• Deploy network monitoring to detect unusual traffic patterns to administrative endpoints

Monitoring Recommendations

• Enable detailed logging for all user management operations in Redaxo CMS
• Set up alerts for new administrator account creation events
• Implement session monitoring to track administrative user sessions and their associated IP addresses
• Regularly audit the user database for unauthorized or suspicious accounts

How to Mitigate CVE-2016-20053

Immediate Actions Required

• Upgrade Redaxo CMS to a version that includes CSRF protection on all state-changing endpoints
• Review and audit all existing administrator accounts for any unauthorized entries
• Implement additional access controls such as IP whitelisting for administrative functions
• Educate administrators about CSRF attacks and safe browsing practices while logged in

Patch Information

Organizations should check the official Redaxo CMS release notes and security advisories for patched versions that address this CSRF vulnerability. Refer to the VulnCheck Security Advisory for additional guidance on remediation.

Workarounds

• Implement a web application firewall (WAF) with CSRF protection rules to filter malicious requests
• Configure the CMS to require re-authentication before performing sensitive operations like creating new users
• Restrict administrative access to specific IP ranges or require VPN access to the admin panel
• Use browser extensions that prevent automatic form submission on untrusted pages
• Log out of the CMS administrative interface when not actively performing administrative tasks

# Example Apache configuration to restrict admin access by IP
<Directory "/path/to/redaxo/redaxo">
    Require ip 192.168.1.0/24
    Require ip 10.0.0.0/8
</Directory>