CVE-2020-2301
📋 TL;DR
The Jenkins Active Directory Plugin vulnerability allows attackers to bypass authentication and log in as any user with any password when using Windows/ADSI mode. This affects Jenkins instances with the vulnerable plugin installed and configured to use Windows/ADSI authentication. Attackers can gain unauthorized access while a successful authentication of the target user is still cached.
💻 Affected Systems
- Jenkins Active Directory Plugin
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of Jenkins instance with administrative privileges, leading to code execution, data theft, and lateral movement within the network.
Likely Case
Unauthorized access to Jenkins with user-level privileges, enabling job manipulation, credential theft, and pipeline compromise.
If Mitigated
Limited impact if proper network segmentation, monitoring, and access controls prevent exploitation attempts.
🎯 Exploit Status
Exploitation requires timing to match cached authentication, but tools exist to automate this. No authentication needed to attempt exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.20
Vendor Advisory: https://www.jenkins.io/security/advisory/2020-11-04/#SECURITY-2123
Restart Required: Yes
Instructions:
1. Update Jenkins Active Directory Plugin to version 2.20 or later via Jenkins Plugin Manager. 2. Restart Jenkins service. 3. Verify plugin version in Manage Jenkins > Plugin Manager.
🔧 Temporary Workarounds
Disable Windows/ADSI Authentication Mode
allSwitch to alternative authentication mode in Jenkins Active Directory Plugin configuration
Navigate to Manage Jenkins > Configure Global Security > Security Realm > Active Directory configuration
Disable Active Directory Plugin
allTemporarily disable the vulnerable plugin until patching is possible
Navigate to Manage Jenkins > Plugin Manager > Installed > Active Directory Plugin > Disable
🧯 If You Can't Patch
- Implement strict network access controls to limit Jenkins access to trusted IPs only
- Enable detailed authentication logging and monitor for suspicious login attempts
🔍 How to Verify
Check if Vulnerable:
Check Jenkins plugin version: Manage Jenkins > Plugin Manager > Installed > Active Directory Plugin. If version is 2.19 or earlier and Windows/ADSI mode is enabled, system is vulnerable.Check Version:
On Jenkins web interface: Manage Jenkins > Plugin Manager > Installed > Active Directory PluginVerify Fix Applied:
Verify Active Directory Plugin version is 2.20 or later in Plugin Manager. Test authentication with invalid credentials to confirm bypass is prevented.📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts followed by successful login with same username
- Successful logins from unusual IP addresses or locations
- Authentication events with mismatched user-agent or timing patterns
Network Indicators:
- Unusual authentication traffic patterns to Jenkins web interface
- Brute-force attempts against Jenkins login endpoints
SIEM Query:
source="jenkins.log" AND ("authentication failure" OR "login attempt") | stats count by src_ip, user | where count > threshold