CVE-2020-2324
📋 TL;DR
The Jenkins CVS Plugin 2.16 and earlier contains an XML External Entity (XXE) vulnerability due to improper XML parser configuration. This allows attackers to read arbitrary files from the Jenkins controller file system, potentially exposing sensitive configuration files, credentials, or source code. Organizations using Jenkins with the CVS plugin are affected.
💻 Affected Systems
- Jenkins CVS Plugin
📦 What is this software?
Cvs by Jenkins
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of Jenkins controller with access to all files on the file system, including credentials, SSH keys, and sensitive configuration data, potentially leading to lateral movement within the network.
Likely Case
Exfiltration of sensitive files from the Jenkins controller, including credentials, configuration files, and potentially source code repositories.
If Mitigated
Limited impact with proper network segmentation and file system permissions restricting access to sensitive files.
🎯 Exploit Status
Exploitation requires authenticated access to Jenkins with permission to configure CVS repositories. XXE vulnerabilities are well-understood and easily weaponized.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.17
Vendor Advisory: https://www.jenkins.io/security/advisory/2020-12-03/#SECURITY-2146
Restart Required: Yes
Instructions:
1. Update Jenkins CVS Plugin to version 2.17 or later via Jenkins Plugin Manager. 2. Restart Jenkins to apply the update. 3. Verify the plugin version in Manage Jenkins > Manage Plugins > Installed tab.
🔧 Temporary Workarounds
Disable CVS Plugin
allRemove or disable the CVS plugin if not required for operations
Manage Jenkins > Manage Plugins > Installed tab > Uninstall CVS Plugin
Restrict User Permissions
allLimit which users can configure CVS repositories to reduce attack surface
Manage Jenkins > Manage and Assign Roles > Role-based Authorization Strategy
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Jenkins from sensitive systems
- Apply file system permissions to restrict access to sensitive files on Jenkins controller
🔍 How to Verify
Check if Vulnerable:
Check Jenkins plugin manager for CVS plugin version. If version is 2.16 or earlier, the system is vulnerable.Check Version:
Check Jenkins web interface at Manage Jenkins > Manage Plugins > Installed tab, or examine $JENKINS_HOME/plugins/cvs/WEB-INF/lib/cvs-*.jar file versionVerify Fix Applied:
Verify CVS plugin version is 2.17 or later in Manage Jenkins > Manage Plugins > Installed tab.📡 Detection & Monitoring
Log Indicators:
- Unusual file access patterns in Jenkins logs
- Multiple failed CVS configuration attempts
- Large XML payloads in CVS-related requests
Network Indicators:
- Outbound connections from Jenkins to unexpected external systems
- Unusual data exfiltration patterns
SIEM Query:
source="jenkins.log" AND ("CVS" OR "cvs") AND ("XXE" OR "external entity" OR "file://" OR "http://")