JetBrains has released critical security patches for TeamCity On-Premises, addressing a major vulnerability that could be exploited without authentication.
Understanding the TeamCity Vulnerability
Identified as CVE-2026-63077, this severe security flaw holds a CVSS score of 9.8. The vulnerability allows attackers to bypass authentication via HTTP/S, leading to potential remote code execution (RCE). The flaw could be manipulated by an unauthenticated user through the TeamCity agent polling protocol.
JetBrains detailed in their advisory that exploiting this vulnerability enables attackers to execute arbitrary operating system commands, leveraging the privileges of the TeamCity server process. This could result in unauthorized access to sensitive TeamCity data, configurations, and credentials, and might even compromise build artifacts and downstream CI/CD pipelines.
Impact and Mitigation Measures
The vulnerability affects all versions of TeamCity On-Premises. While JetBrains has implemented mitigations for TeamCity Cloud instances, the company confirmed no known exploitation of the flaw in the wild. To counteract the risk, JetBrains has issued fixes in versions 2025.11.7 and 2026.1.3, alongside a security patch plugin for version 2017.1 and above for those unable to upgrade.
Users are strongly advised to promptly upgrade to the latest version or apply the security patch plugin, which specifically addresses this CVE. Additionally, JetBrains recommends measures such as restricting access to internet-facing servers, using minimal required operating system privileges, and employing VPNs or other security protocols to shield against unauthorized access.
Best Practices for Secure TeamCity Usage
For enhanced security, JetBrains advises running TeamCity servers on dedicated hosts, distinct from build agents, to prevent potential breaches. By adhering to these guidelines, users can significantly mitigate the risk posed by this vulnerability.
In related security news, other notable vulnerabilities have been addressed in products like Chrome and VMware ESXi, underscoring the ongoing importance of vigilance in cybersecurity practices.
As cyber threats evolve, staying informed and taking proactive steps to secure software environments remains crucial. Users are encouraged to keep their systems updated with the latest security patches to protect against emerging threats.
