CVE-2021-37553
📋 TL;DR
This vulnerability in JetBrains YouTrack uses an insecure pseudo-random number generator (PRNG) that could allow attackers to predict generated values. This affects YouTrack instances before version 2021.2.16363, potentially compromising security mechanisms that rely on random values like session tokens or cryptographic operations.
💻 Affected Systems
- JetBrains YouTrack
📦 What is this software?
Youtrack by Jetbrains
⚠️ Risk & Real-World Impact
Worst Case
Attackers could predict session tokens, authentication tokens, or cryptographic keys, leading to complete system compromise, data theft, or privilege escalation.
Likely Case
Predictable values in security-sensitive operations could enable session hijacking, authentication bypass, or data integrity violations.
If Mitigated
With proper network segmentation and access controls, impact would be limited to the YouTrack application itself rather than broader infrastructure.
🎯 Exploit Status
Exploitation requires understanding of PRNG weaknesses and access to observe generated values. No public exploit code has been identified.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2021.2.16363 or later
Vendor Advisory: https://blog.jetbrains.com/blog/2021/08/05/jetbrains-security-bulletin-q2-2021/
Restart Required: Yes
Instructions:
1. Backup your YouTrack instance and data. 2. Download YouTrack version 2021.2.16363 or later from JetBrains. 3. Follow JetBrains upgrade documentation for your deployment method (Docker, JAR, etc.). 4. Restart the YouTrack service.
🔧 Temporary Workarounds
Network Isolation
allRestrict network access to YouTrack to trusted IP addresses only
Use firewall rules to limit inbound connections to YouTrack port (typically 8080/8443) from authorized networks
🧯 If You Can't Patch
- Implement strict network segmentation to isolate YouTrack from critical systems
- Monitor for unusual authentication patterns or session anomalies
🔍 How to Verify
Check if Vulnerable:
Check YouTrack version in Administration → Global Settings → AboutCheck Version:
For Docker: docker inspect youtrack-container | grep -i version; For JAR: java -jar youtrack.jar --versionVerify Fix Applied:
Confirm version is 2021.2.16363 or higher in Administration → Global Settings → About📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login from same IP
- Unusual session creation patterns
Network Indicators:
- Unusual traffic patterns to YouTrack authentication endpoints
- Multiple session token requests from single source
SIEM Query:
source="youtrack" AND (event="authentication" OR event="session") | stats count by src_ip, user