CVE-2020-15831 in TeamCity
Summary
by MITRE
JetBrains TeamCity before 2019.2.3 is vulnerable to reflected XSS in the administration UI.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 08/09/2020
JetBrains TeamCity versions prior to 2019.2.3 contain a reflected cross-site scripting vulnerability that affects the administration user interface. This vulnerability allows remote attackers to inject malicious scripts into the web application through carefully crafted input parameters that are then reflected back to users without proper sanitization or encoding. The flaw exists in the way the application processes and displays user-supplied input within the administrative interface, creating an opportunity for attackers to execute arbitrary JavaScript code in the context of a victim's browser session.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding mechanisms within TeamCity's administrative web components. When administrators or authenticated users navigate to specific pages within the administration UI, the application fails to properly escape or filter user-controllable parameters before rendering them in HTML responses. This allows an attacker to craft malicious URLs containing script payloads that, when executed by a victim's browser, can perform actions such as stealing session cookies, redirecting users to malicious sites, or performing unauthorized administrative operations on behalf of the victim. The vulnerability is classified as reflected XSS because the malicious script is reflected off the web server in response to the user's request rather than being stored on the server.
The operational impact of this vulnerability is significant for organizations using affected TeamCity versions, as it provides attackers with a potential entry point for privilege escalation and persistent access to the build server infrastructure. An attacker who successfully exploits this vulnerability can potentially gain administrative privileges within the TeamCity environment, access sensitive configuration data, modify build processes, or exfiltrate source code and credentials stored within the system. The reflected nature of the vulnerability means that exploitation typically requires social engineering to convince administrators to click on malicious links, but once executed, the attack can have far-reaching consequences for continuous integration and deployment pipelines. This vulnerability directly relates to CWE-79 which describes improper neutralization of input during web page generation, and aligns with ATT&CK technique T1211 for lateral movement through the exploitation of web application vulnerabilities.
Organizations should immediately upgrade to TeamCity version 2019.2.3 or later to remediate this vulnerability, as JetBrains has released patches specifically addressing the reflected XSS issue in their administrative interface. Additionally, implementing proper input validation and output encoding mechanisms, such as using Content Security Policy headers, can provide additional defense-in-depth measures. Network segmentation and monitoring for suspicious user activity within the TeamCity administration interface should also be considered as mitigation strategies. Regular security assessments and vulnerability scanning of the TeamCity installation, including checking for outdated components and plugins, will help prevent similar issues from arising in the future. Organizations should also implement proper access controls and authentication mechanisms to reduce the potential impact of any successful exploitation attempts, as the vulnerability requires authentication to the administrative interface but could potentially be leveraged for privilege escalation once accessed.