CVE-2021-37597
📋 TL;DR
CVE-2021-37597 is an authentication bypass vulnerability in WP Cerber security plugin for WordPress that allows attackers to bypass multi-factor authentication (MFA) by manipulating the wordpress_logged_in_[hash] cookie. This affects WordPress sites using WP Cerber versions before 8.9.3 for authentication security.
💻 Affected Systems
- WP Cerber Security, Anti-spam & Malware Scan
📦 What is this software?
Wp Cerber by Wpcerber
⚠️ Risk & Real-World Impact
Worst Case
Complete site compromise allowing attackers to gain administrative access, install backdoors, steal sensitive data, and deface or take down the website.
Likely Case
Unauthorized access to user accounts, privilege escalation, and potential data exfiltration from compromised accounts.
If Mitigated
Limited impact with proper network segmentation, strong monitoring, and additional authentication layers beyond WP Cerber.
🎯 Exploit Status
Exploitation requires valid user credentials but bypasses MFA requirements. Attackers need to manipulate authentication cookies after initial login.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 8.9.3 and later
Vendor Advisory: https://wpcerber.com/
Restart Required: No
Instructions:
1. Log into WordPress admin panel. 2. Navigate to Plugins → Installed Plugins. 3. Find WP Cerber Security plugin. 4. Click 'Update Now' if update available. 5. If no update shows, download version 8.9.3+ from WordPress repository and manually update.
🔧 Temporary Workarounds
Disable WP Cerber MFA
allTemporarily disable WP Cerber's MFA functionality while maintaining other security features
Implement Web Application Firewall Rules
allBlock suspicious cookie manipulation attempts at the WAF level
🧯 If You Can't Patch
- Implement additional authentication layer (e.g., web server authentication, IP whitelisting)
- Monitor for unusual authentication patterns and cookie manipulation attempts
🔍 How to Verify
Check if Vulnerable:
Check WP Cerber plugin version in WordPress admin panel under Plugins → Installed PluginsCheck Version:
wp plugin list --name=wp-cerber --field=versionVerify Fix Applied:
Verify WP Cerber version is 8.9.3 or higher and test MFA functionality📡 Detection & Monitoring
Log Indicators:
- Multiple failed MFA attempts followed by successful login with manipulated cookies
- Unusual user agent patterns during authentication
Network Indicators:
- HTTP requests with manipulated wordpress_logged_in_* cookies
- Authentication requests bypassing expected MFA flow
SIEM Query:
source="wordpress.log" AND ("wp-cerber" OR "authentication") AND ("cookie" OR "wordpress_logged_in") AND status=200🔗 References
- https://github.com/fireeye/Vulnerability-Disclosures
- https://github.com/fireeye/Vulnerability-Disclosures/blob/master/FEYE-2021-0023/FEYE-2021-0023.md
- https://github.com/fireeye/Vulnerability-Disclosures
- https://github.com/fireeye/Vulnerability-Disclosures/blob/master/FEYE-2021-0023/FEYE-2021-0023.md
