CVE-2024-41827: JetBrains TeamCity Auth Bypass Vulnerability

CVE-2024-41827 Overview

CVE-2024-41827 is a critical session expiration vulnerability in JetBrains TeamCity that allows access tokens to continue functioning after they have been deleted or expired. This improper session expiration flaw (CWE-613) enables attackers who have obtained valid access tokens to maintain persistent unauthorized access to TeamCity instances, even after administrators have attempted to revoke access or tokens have reached their intended expiration date.

Critical Impact

Attackers with previously compromised or leaked access tokens can maintain persistent unauthorized access to TeamCity CI/CD pipelines, potentially compromising build processes, source code, and deployment credentials even after token revocation attempts.

Affected Products

• JetBrains TeamCity versions prior to 2024.07

Discovery Timeline

• 2024-07-22 - CVE-2024-41827 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-41827

Vulnerability Analysis

This vulnerability stems from improper session expiration handling within JetBrains TeamCity's access token management system. When access tokens are deleted by administrators or reach their configured expiration time, the system fails to properly invalidate these credentials. The token validation mechanism does not correctly check against the revocation status or expiration timestamp stored in the backend, allowing previously valid tokens to continue authenticating API requests.

The flaw is particularly dangerous in CI/CD environments where access tokens are commonly used for automation, service accounts, and integration with external systems. TeamCity's network-accessible API surface means that any attacker who has previously obtained a token—through credential leaks, phishing, or other means—can maintain access indefinitely until the vulnerable version is patched.

Root Cause

The root cause is classified under CWE-613 (Insufficient Session Expiration). The TeamCity token validation logic fails to properly synchronize with the token lifecycle management system. When a token is marked as deleted or expired in the database, the authentication layer does not immediately honor this status change, creating a window where revoked tokens remain functional.

Attack Vector

The vulnerability is exploited over the network without requiring any user interaction or prior privileges. An attacker who possesses a compromised access token can continue to authenticate to the TeamCity API and web interface even after:

1. An administrator explicitly deletes the token from the user's profile
2. The token reaches its configured expiration date
3. The associated user account is disabled or deleted

This allows persistent access to sensitive CI/CD resources including build configurations, deployment pipelines, environment variables containing secrets, and integration credentials for connected systems like version control and artifact repositories.

Detection Methods for CVE-2024-41827

Indicators of Compromise

• API authentication events using tokens that have been previously revoked or should have expired
• Unusual or unexpected access patterns from service accounts or integrations after credential rotation
• Authentication logs showing successful access from tokens that administrators believed were invalidated
• Access from unexpected IP addresses or geographic locations using automation tokens

Detection Strategies

• Review TeamCity audit logs for authentication events and cross-reference with token lifecycle events
• Implement alerting on API access using tokens that were recently deleted or are past their expiration date
• Monitor for authentication patterns that persist after security credential rotations
• Enable verbose logging for token validation operations to identify tokens that should be rejected

Monitoring Recommendations

• Establish baseline authentication patterns for all service accounts and automation tokens
• Implement real-time alerting for any authentication events that occur after token revocation actions
• Deploy network monitoring to track TeamCity API traffic volumes and patterns for anomalies
• Regularly audit active tokens and compare against expected integrations and service accounts

How to Mitigate CVE-2024-41827

Immediate Actions Required

• Upgrade JetBrains TeamCity to version 2024.07 or later immediately
• Rotate all existing access tokens after upgrading to ensure old tokens cannot be misused
• Audit recent authentication logs for any suspicious access patterns using tokens that should have been expired
• Review and revoke any unnecessary or overly permissioned access tokens

Patch Information

JetBrains has addressed this vulnerability in TeamCity version 2024.07. Organizations should update to this version or later to remediate the session expiration flaw. The security advisory is available on the JetBrains Privacy and Security Issues Fixed page.

Workarounds

• If immediate patching is not possible, consider temporarily disabling token-based authentication and using alternative authentication methods
• Implement network-level access controls to restrict TeamCity API access to trusted IP ranges only
• Enable additional authentication factors where supported to reduce the impact of compromised tokens
• Monitor all token-based authentication events closely and investigate any unexpected access patterns