CVE-2019-12842 in TeamCity
Summary
by MITRE
A reflected XSS on a user page was detected on one of the JetBrains TeamCity pages. The issue was fixed in TeamCity 2018.2.2.
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Analysis
by VulDB Data Team • 06/30/2020
The vulnerability identified as CVE-2019-12842 represents a reflected cross-site scripting flaw discovered within JetBrains TeamCity's web interface. This security weakness specifically affected user pages within the TeamCity continuous integration and deployment platform, which is widely used by organizations for automating software build processes and managing development workflows. The vulnerability emerged due to insufficient input validation and output encoding mechanisms within the web application's user-facing components, creating an exploitable entry point for malicious actors to inject client-side scripts.
The technical nature of this reflected XSS vulnerability stems from the application's failure to properly sanitize user-supplied input parameters before incorporating them into web page responses. When a user visited a maliciously crafted URL containing script code within query parameters or other input fields, the TeamCity application would reflect this malicious content back to the user's browser without adequate sanitization. This reflected behavior allows attackers to execute arbitrary JavaScript code within the victim's browser context, potentially enabling session hijacking, credential theft, or redirection to malicious sites. The vulnerability falls under CWE-79 which specifically addresses Cross-Site Scripting flaws in software applications.
The operational impact of this vulnerability extends beyond simple script execution as it could compromise the integrity of the entire TeamCity environment. Since TeamCity serves as a central hub for development activities including build automation, deployment management, and project tracking, successful exploitation could allow attackers to gain unauthorized access to sensitive build configurations, source code repositories, and deployment credentials. The reflected nature of the vulnerability means that exploitation requires social engineering to convince users to click malicious links, making it particularly dangerous in environments where developers frequently interact with external links or receive notifications from untrusted sources. This vulnerability aligns with ATT&CK technique T1566 which covers social engineering tactics used to gain initial access to systems.
JetBrains addressed this vulnerability by implementing proper input validation and output encoding mechanisms within TeamCity 2018.2.2, ensuring that all user-supplied parameters are properly sanitized before being rendered in web responses. The fix typically involves applying HTML encoding to dynamic content, implementing Content Security Policy headers, and strengthening input validation routines to prevent malicious script injection. Organizations utilizing TeamCity should prioritize updating to version 2018.2.2 or later to mitigate this risk, while also implementing additional security measures such as network segmentation, monitoring for suspicious user behavior, and regular security assessments of web applications. The vulnerability demonstrates the critical importance of maintaining up-to-date security patches in development environments where sensitive operational data is processed and managed.