CVE-2024-23917
📋 TL;DR
This critical vulnerability in JetBrains TeamCity allows attackers to bypass authentication mechanisms and achieve remote code execution (RCE) on affected servers. Organizations using TeamCity versions before 2023.11.3 for CI/CD pipelines are at risk of complete system compromise.
💻 Affected Systems
- JetBrains TeamCity
📦 What is this software?
Teamcity by Jetbrains
⚠️ Risk & Real-World Impact
Worst Case
Full system takeover: attackers gain administrative access, execute arbitrary code, steal source code, deploy malicious builds, and pivot to internal networks.
Likely Case
Unauthorized access leading to source code theft, build pipeline manipulation, and deployment of malicious artifacts to production environments.
If Mitigated
Limited impact with proper network segmentation and strict access controls, but authentication bypass still exposes sensitive CI/CD data.
🎯 Exploit Status
Multiple public proof-of-concept exploits exist. The authentication bypass makes exploitation trivial for attackers with network access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2023.11.3 or later
Vendor Advisory: https://www.jetbrains.com/privacy-security/issues-fixed/
Restart Required: Yes
Instructions:
1. Backup TeamCity configuration and data. 2. Download TeamCity 2023.11.3 or later from JetBrains website. 3. Stop TeamCity service. 4. Install the updated version following JetBrains upgrade guide. 5. Restart TeamCity service. 6. Verify successful upgrade.
🔧 Temporary Workarounds
Network Access Restriction
allRestrict network access to TeamCity instances using firewall rules to only allow trusted IP addresses.
# Example Linux iptables rule: iptables -A INPUT -p tcp --dport 8111 -s TRUSTED_IP -j ACCEPT
# Example Windows Firewall: New-NetFirewallRule -DisplayName "TeamCity Restrict" -Direction Inbound -LocalPort 8111 -RemoteAddress TRUSTED_IP -Protocol TCP -Action Allow
🧯 If You Can't Patch
- Immediately isolate TeamCity servers from internet access and restrict to internal networks only.
- Implement strict network segmentation and monitor all TeamCity traffic for suspicious authentication attempts.
🔍 How to Verify
Check if Vulnerable:
Check TeamCity version via web interface (Admin → Server Administration) or by examining the TeamCity server logs for version information.Check Version:
# Check via TeamCity API: curl -s http://teamcity-server:8111/app/rest/server | grep -o '"version":"[^"]*' | cut -d'"' -f4Verify Fix Applied:
Confirm version is 2023.11.3 or later in Admin → Server Administration. Test authentication bypass attempts should fail.📡 Detection & Monitoring
Log Indicators:
- Unusual authentication patterns
- Failed login attempts followed by successful access
- Unexpected administrative actions from new IP addresses
Network Indicators:
- HTTP requests to authentication endpoints without proper credentials
- Unusual outbound connections from TeamCity server
SIEM Query:
source="teamcity.log" AND ("authentication bypass" OR "unauthorized access" OR "admin action from new IP")