CVE-2024-41827
📋 TL;DR
This vulnerability allows access tokens in JetBrains TeamCity to remain functional after they have been deleted or expired, creating an authentication bypass. Any TeamCity server with access tokens configured is affected, potentially allowing unauthorized access to CI/CD pipelines and build systems.
💻 Affected Systems
- JetBrains TeamCity
📦 What is this software?
Teamcity by Jetbrains
⚠️ Risk & Real-World Impact
Worst Case
Attackers with previously obtained tokens can maintain persistent access to TeamCity instances, potentially compromising source code, build artifacts, and deployment pipelines, leading to supply chain attacks or production system compromise.
Likely Case
Former employees or contractors with valid tokens retain access after their accounts are disabled, allowing unauthorized viewing or modification of build configurations and source code.
If Mitigated
With proper network segmentation and monitoring, impact is limited to unauthorized access within the TeamCity environment, though sensitive data exposure remains possible.
🎯 Exploit Status
Exploitation requires possession of a previously valid access token. No special tools or techniques needed beyond using the token in API calls.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2024.07
Vendor Advisory: https://www.jetbrains.com/privacy-security/issues-fixed/
Restart Required: Yes
Instructions:
1. Backup TeamCity configuration and data. 2. Download TeamCity 2024.07 or later from JetBrains website. 3. Stop TeamCity service. 4. Install the new version following JetBrains upgrade guide. 5. Restart TeamCity service. 6. Verify all functionality.
🔧 Temporary Workarounds
Rotate All Access Tokens
allManually revoke and regenerate all access tokens to invalidate potentially compromised tokens.
Navigate to TeamCity Administration > Access Tokens, revoke all existing tokens, then create new tokens as needed.
Network Access Restrictions
allRestrict TeamCity access to trusted IP ranges only.
Configure firewall rules to allow TeamCity access only from authorized networks and IP addresses.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate TeamCity from production systems
- Enable comprehensive logging and monitoring for suspicious token usage patterns
🔍 How to Verify
Check if Vulnerable:
Check TeamCity version in Administration > Server Administration > Server Configuration. If version is below 2024.07, system is vulnerable.Check Version:
Check TeamCity web interface at Administration > Server Administration > Server ConfigurationVerify Fix Applied:
After upgrading to 2024.07 or later, test that deleted tokens no longer work by attempting API calls with revoked tokens.📡 Detection & Monitoring
Log Indicators:
- API requests using tokens that should be expired or revoked
- Unauthorized access attempts from unexpected IPs using valid tokens
Network Indicators:
- Unusual API call patterns from external IPs
- Traffic to TeamCity from unexpected sources
SIEM Query:
source="teamcity" AND (token_revoked="true" OR token_expired="true") AND action="api_call"