CVE-2024-27199: JetBrains TeamCity Path Traversal Flaw

CVE-2024-27199 Overview

CVE-2024-27199 is a path traversal vulnerability in JetBrains TeamCity, a popular continuous integration and continuous deployment (CI/CD) server used by development teams worldwide. This vulnerability allows unauthenticated attackers to perform limited administrative actions on affected TeamCity instances by exploiting improper path validation in the web server component.

Critical Impact

Unauthenticated attackers can leverage path traversal techniques to bypass access controls and perform limited administrative operations on TeamCity servers, potentially compromising build pipelines and development infrastructure.

Affected Products

• JetBrains TeamCity versions before 2023.11.4
• All TeamCity installations accessible via network without updated patches

Discovery Timeline

• 2024-03-04 - CVE CVE-2024-27199 published to NVD
• 2025-05-30 - Last updated in NVD database

Technical Details for CVE-2024-27199

Vulnerability Analysis

This path traversal vulnerability (CWE-22, CWE-23) in JetBrains TeamCity stems from insufficient validation of user-supplied input in URL path handling. The vulnerability enables attackers to craft malicious requests that traverse directory structures, allowing access to administrative functionality that should be protected by authentication mechanisms.

The exploitation of this vulnerability does not require any authentication or user interaction, making it particularly dangerous for internet-exposed TeamCity instances. According to Dark Reading's analysis, mass exploitation campaigns have been observed targeting this vulnerability, with attackers creating rogue accounts on compromised servers.

Root Cause

The root cause of CVE-2024-27199 is improper path validation in TeamCity's web server component. The application fails to properly sanitize path traversal sequences (such as ../) in HTTP requests, allowing attackers to escape the intended directory structure and access protected administrative endpoints. This falls under CWE-22 (Improper Limitation of a Pathname to a Restricted Directory) and CWE-23 (Relative Path Traversal).

Attack Vector

The vulnerability is exploitable over the network without authentication. An attacker can send specially crafted HTTP requests containing path traversal sequences to a vulnerable TeamCity server. By manipulating URL paths, the attacker can bypass access controls and invoke administrative functions that would normally require authentication.

The attack methodology involves:

1. Identifying an exposed TeamCity instance
2. Crafting HTTP requests with path traversal sequences targeting administrative endpoints
3. Executing limited administrative actions such as modifying server settings or accessing sensitive configuration data

Detection Methods for CVE-2024-27199

Indicators of Compromise

• Unusual HTTP requests containing path traversal sequences (../, ..%2f, %2e%2e/) in TeamCity web server logs
• Unauthorized administrative actions in TeamCity audit logs
• Creation of unexpected user accounts with administrative privileges
• Modifications to TeamCity server configuration without authorized changes

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block path traversal patterns in incoming requests
• Monitor TeamCity access logs for requests containing encoded or unencoded directory traversal sequences
• Configure SIEM alerts for administrative actions performed without corresponding authenticated sessions
• Deploy endpoint detection solutions to monitor TeamCity server processes for anomalous behavior

Monitoring Recommendations

• Enable comprehensive audit logging on all TeamCity instances
• Monitor network traffic for suspicious patterns targeting TeamCity's web interface
• Implement anomaly detection for administrative API calls from unexpected sources
• Review TeamCity user accounts and permissions regularly for unauthorized changes

How to Mitigate CVE-2024-27199

Immediate Actions Required

• Upgrade JetBrains TeamCity to version 2023.11.4 or later immediately
• Restrict network access to TeamCity instances using firewall rules until patching is complete
• Audit existing TeamCity user accounts for unauthorized entries
• Review TeamCity audit logs for evidence of exploitation attempts
• Consider temporarily taking internet-exposed TeamCity servers offline until patched

Patch Information

JetBrains has released TeamCity version 2023.11.4 which addresses this vulnerability. Organizations should apply this update as the primary remediation measure. The security advisory and patch details are available at the JetBrains Security Issues Fixed page.

Workarounds

• Place TeamCity servers behind a reverse proxy with path traversal filtering capabilities
• Implement network segmentation to limit access to TeamCity servers from trusted networks only
• Configure web application firewall rules to block requests containing path traversal sequences
• Disable external network access to TeamCity instances if remote access is not required

# Example: iptables rule to restrict TeamCity access to internal network only
iptables -A INPUT -p tcp --dport 8111 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 8111 -j DROP