CVE-2021-31914
📋 TL;DR
This vulnerability allows attackers to execute arbitrary code on JetBrains TeamCity servers running on Windows. It affects TeamCity installations before version 2020.2.4 on Windows operating systems, potentially compromising the entire CI/CD pipeline.
💻 Affected Systems
- JetBrains TeamCity
📦 What is this software?
Teamcity by Jetbrains
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the TeamCity server, allowing attackers to steal source code, deploy malicious builds, pivot to internal networks, and maintain persistent access.
Likely Case
Attackers gain control of the TeamCity server to execute arbitrary commands, potentially modifying build processes or stealing credentials.
If Mitigated
Limited impact with proper network segmentation and access controls, but still significant if exploited.
🎯 Exploit Status
Exploitation details are not publicly documented, but the high CVSS score suggests significant impact potential.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2020.2.4 or later
Vendor Advisory: https://blog.jetbrains.com/blog/2021/05/07/jetbrains-security-bulletin-q1-2021/
Restart Required: Yes
Instructions:
1. Backup TeamCity configuration and data. 2. Download TeamCity 2020.2.4 or later from JetBrains website. 3. Stop TeamCity service. 4. Install the updated version. 5. Restart TeamCity service. 6. Verify functionality.
🔧 Temporary Workarounds
Network Segmentation
allRestrict network access to TeamCity server to only trusted IPs and users.
Operating System Migration
allMigrate TeamCity installation from Windows to Linux or macOS if possible.
🧯 If You Can't Patch
- Implement strict network access controls and firewall rules to limit TeamCity server exposure.
- Monitor TeamCity server logs and network traffic for suspicious activity.
🔍 How to Verify
Check if Vulnerable:
Check TeamCity version in Administration → Server Administration → Server Information. If version is below 2020.2.4 and OS is Windows, system is vulnerable.Check Version:
Check TeamCity web interface at Administration → Server Administration → Server InformationVerify Fix Applied:
Verify TeamCity version is 2020.2.4 or higher in Administration → Server Administration → Server Information.📡 Detection & Monitoring
Log Indicators:
- Unusual process execution on TeamCity server
- Suspicious authentication attempts
- Unexpected system modifications
Network Indicators:
- Unusual outbound connections from TeamCity server
- Suspicious inbound traffic to TeamCity ports
SIEM Query:
source="teamcity" AND (event_type="process_execution" OR event_type="authentication_failure")