CVE-2020-26105
📋 TL;DR
CVE-2020-26105 is an authentication bypass vulnerability in cPanel's chkservd service that uses insecure test credentials on templated virtual machines. Attackers can exploit these hardcoded credentials to gain unauthorized access to affected systems. This affects cPanel installations on templated VMs before version 88.0.3.
💻 Affected Systems
- cPanel
📦 What is this software?
Cpanel by Cpanel
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to execute arbitrary code, access sensitive data, and pivot to other systems in the environment.
Likely Case
Unauthorized access to the cPanel system leading to privilege escalation, data theft, and potential service disruption.
If Mitigated
Limited impact with proper network segmentation and access controls preventing lateral movement even if initial access is gained.
🎯 Exploit Status
Exploitation requires knowledge of the hardcoded test credentials, which may be discoverable through reverse engineering or information disclosure.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 88.0.3
Vendor Advisory: https://docs.cpanel.net/changelogs/88-change-log/
Restart Required: Yes
Instructions:
1. Log into cPanel WHM. 2. Navigate to 'Update cPanel & WHM'. 3. Select 'Update to latest version'. 4. Confirm update to version 88.0.3 or later. 5. Restart services as prompted.
🔧 Temporary Workarounds
Remove test credentials
linuxManually locate and remove insecure chkservd test credentials from the system
# Check for test credential files in chkservd configuration
find /etc/chkserv.d/ -type f -exec grep -l 'test.*credential' {} \;
# Review and remove any test credential configurations
🧯 If You Can't Patch
- Implement strict network access controls to limit cPanel access to trusted IP addresses only
- Monitor authentication logs for unusual access patterns and failed login attempts
🔍 How to Verify
Check if Vulnerable:
Check cPanel version: if below 88.0.3 and running on templated VM, system is vulnerable. Also check for test credential files in /etc/chkserv.d/Check Version:
cat /usr/local/cpanel/versionVerify Fix Applied:
Verify cPanel version is 88.0.3 or later using 'cat /usr/local/cpanel/version' and confirm no test credentials exist in chkservd configuration📡 Detection & Monitoring
Log Indicators:
- Unusual authentication attempts to chkservd service
- Access from unexpected IP addresses to cPanel services
- Failed login attempts using test credential patterns
Network Indicators:
- Unexpected connections to cPanel ports (2086, 2087, 2083) from untrusted sources
- Traffic patterns indicating credential brute forcing
SIEM Query:
source="cpanel.log" AND ("authentication failed" OR "invalid credentials") AND (process="chkservd" OR service="chkservd")