CVE-2022-20621: Jenkins Metrics Information Disclosure Flaw

CVE-2022-20621 Overview

CVE-2022-20621 is a sensitive data exposure vulnerability affecting the Jenkins Metrics Plugin version 4.0.2.8 and earlier. The vulnerability exists because the plugin stores an access key unencrypted in its global configuration file on the Jenkins controller, potentially allowing unauthorized users with access to the Jenkins controller file system to view and extract the sensitive credential.

Critical Impact

Unauthorized users with file system access to the Jenkins controller can retrieve plaintext access keys, potentially leading to unauthorized access to metrics endpoints and further compromise of the Jenkins environment.

Affected Products

• Jenkins Metrics Plugin versions 4.0.2.8 and earlier

Discovery Timeline

• 2022-01-12 - CVE-2022-20621 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-20621

Vulnerability Analysis

This vulnerability is classified under CWE-522 (Insufficiently Protected Credentials). The Jenkins Metrics Plugin fails to properly encrypt sensitive access keys when storing them in the global configuration file. When the plugin is configured on a Jenkins controller, the access key used for authenticating to metrics endpoints is written to disk in plaintext format.

This insecure storage mechanism creates a significant risk in shared environments or scenarios where multiple users have varying levels of access to the Jenkins controller file system. An attacker with local access privileges could simply read the configuration file to extract the access key without needing to bypass any cryptographic protections.

Root Cause

The root cause of this vulnerability lies in the plugin's failure to implement proper credential encryption before persisting sensitive data to the file system. Jenkins provides APIs for securely storing credentials using encryption, but the Metrics Plugin did not utilize these mechanisms for the access key storage. Instead, the access key is stored as plaintext in the plugin's global configuration XML file on the Jenkins controller.

Attack Vector

The attack vector is local, requiring the attacker to have some level of access to the Jenkins controller file system. An attacker could exploit this vulnerability through several means:

1. Direct file system access as a legitimate but lower-privileged user on the Jenkins server
2. Access through compromised backup systems that contain Jenkins configuration files
3. Exploitation of another vulnerability that grants file read access to the Jenkins controller

Once the attacker gains access to the configuration file, extracting the plaintext access key is trivial. The attacker can then use this key to authenticate to Jenkins Metrics endpoints, potentially gaining insights into system performance data or using the compromised credentials for lateral movement if the same credentials are reused elsewhere.

Detection Methods for CVE-2022-20621

Indicators of Compromise

• Unusual access patterns to Jenkins configuration directories or files
• Unexpected reads of the Metrics Plugin configuration file by unauthorized users or processes
• Authentication attempts to metrics endpoints from unusual IP addresses or user accounts
• Audit log entries showing file system access to Jenkins controller configuration directories

Detection Strategies

• Implement file integrity monitoring on Jenkins configuration directories to detect unauthorized access
• Review Jenkins file system access logs for suspicious read operations targeting plugin configuration files
• Monitor authentication logs for the metrics endpoints for anomalous access patterns
• Conduct periodic audits of users and processes with access to the Jenkins controller file system

Monitoring Recommendations

• Enable detailed audit logging for file system operations on the Jenkins controller
• Configure alerting for access to sensitive configuration directories outside of normal maintenance windows
• Implement role-based access controls and monitor for privilege escalation attempts
• Use SentinelOne Singularity Platform to detect and alert on suspicious file access patterns on Jenkins servers

How to Mitigate CVE-2022-20621

Immediate Actions Required

• Upgrade the Jenkins Metrics Plugin to a version newer than 4.0.2.8 that addresses this vulnerability
• Restrict file system access to the Jenkins controller to only essential personnel and processes
• Rotate the access key used by the Metrics Plugin after upgrading to ensure any potentially compromised keys are invalidated
• Review access logs to determine if the configuration file containing the plaintext key was accessed by unauthorized parties

Patch Information

Jenkins has released a security advisory addressing this vulnerability. Users should update to the latest version of the Metrics Plugin that properly encrypts the access key in the configuration file. Detailed information about the patch can be found in the Jenkins Security Advisory SECURITY-1624.

Workarounds

• Implement strict file system permissions on the Jenkins controller to limit access to configuration files
• Use operating system-level access controls to restrict which users can read the Jenkins home directory
• Consider using Jenkins' built-in credential management system to store sensitive keys rather than plugin-specific configuration
• Monitor and audit file access to the Jenkins configuration directory as an interim measure until the plugin can be updated

# Restrict file permissions on Jenkins configuration directory
chmod 700 /var/lib/jenkins
chown -R jenkins:jenkins /var/lib/jenkins

# Verify Metrics Plugin version
java -jar jenkins-cli.jar -s http://localhost:8080/ list-plugins | grep metrics