CVE-2025-59476
📋 TL;DR
This vulnerability allows attackers who can control log message content in Jenkins to insert line break characters followed by forged log messages. This could mislead administrators reviewing log output by making malicious entries appear legitimate. Affects Jenkins 2.527 and earlier, and LTS 2.516.2 and earlier.
💻 Affected Systems
- Jenkins
📦 What is this software?
Jenkins by Jenkins
Jenkins by Jenkins
⚠️ Risk & Real-World Impact
Worst Case
Attackers could forge critical log entries to hide real attacks, misdirect investigations, or create false alerts that trigger unnecessary actions.
Likely Case
Attackers with existing access could insert misleading log entries to cover tracks or create confusion during incident response.
If Mitigated
With proper log review procedures and integrity controls, forged entries would be detected as anomalies.
🎯 Exploit Status
Exploitation requires ability to inject content into log messages, which typically requires authenticated access or plugin vulnerabilities.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Jenkins 2.528, LTS 2.516.3
Vendor Advisory: https://www.jenkins.io/security/advisory/2025-09-17/#SECURITY-3424
Restart Required: No
Instructions:
1. Backup Jenkins configuration and data. 2. Upgrade to Jenkins 2.528 or LTS 2.516.3. 3. Verify upgrade completed successfully. 4. Monitor logs for any anomalies.
🔧 Temporary Workarounds
Log sanitization filter
allImplement custom log filtering to strip or escape line break characters from user-controlled content
Implement custom LogFilter extension in Jenkins
🧯 If You Can't Patch
- Implement strict access controls to limit who can write to logs
- Deploy log integrity monitoring to detect forged entries
🔍 How to Verify
Check if Vulnerable:
Check Jenkins version via Manage Jenkins > About Jenkins or via CLI: java -jar jenkins.war --versionCheck Version:
java -jar jenkins.war --versionVerify Fix Applied:
Verify version is 2.528 or higher (or LTS 2.516.3 or higher) and test log injection attempts are properly sanitized📡 Detection & Monitoring
Log Indicators:
- Unusual line break patterns in logs
- Log entries with mismatched timestamps or sources
- Suspicious log content following line breaks
Network Indicators:
- None specific to this vulnerability
SIEM Query:
source="jenkins.log" AND (message="\n\n" OR message="\r\n")