CVE-2020-15830 in TeamCity
Summary
by MITRE
JetBrains TeamCity before 2019.2.3 is vulnerable to stored XSS in the administration UI.
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Analysis
by VulDB Data Team • 08/09/2020
JetBrains TeamCity versions prior to 2019.2.3 contain a stored cross-site scripting vulnerability that allows attackers to inject malicious scripts into the administration user interface. This vulnerability specifically affects the web-based administrative console where users can configure build settings, manage projects, and control various system parameters. The flaw enables an attacker to store malicious JavaScript code within the application's persistent storage, which then executes whenever authenticated administrators access the affected pages. The vulnerability arises from insufficient input validation and output sanitization within the TeamCity administration interface, particularly when handling user-supplied data that gets rendered back to the browser without proper encoding or filtering. This stored XSS vulnerability represents a critical security risk as it can be exploited by attackers who gain access to any account with administrative privileges, potentially leading to full system compromise. The attack vector typically involves an authenticated user with administrative rights manipulating configuration parameters or project settings where input fields are not properly sanitized before being stored and subsequently displayed.
The technical implementation of this vulnerability stems from TeamCity's handling of user-provided data within its administrative web interface. When administrators configure build parameters, project names, or other configurable elements, the application fails to adequately sanitize input before storing it in the database. The stored data is then retrieved and rendered in the browser without proper HTML escaping or context-appropriate encoding. This allows attackers to inject malicious JavaScript payloads that execute in the context of the victim's browser session. The vulnerability is classified as a stored XSS due to the persistence of the malicious code within the application's backend storage system. Attackers can leverage this flaw to steal session cookies, redirect users to malicious sites, modify administrative settings, or perform actions on behalf of the compromised administrator. The attack requires minimal privileges since any user with administrative access can exploit this vulnerability, making it particularly dangerous in environments where multiple administrators have access to the system.
The operational impact of CVE-2020-15830 extends beyond simple script execution, as it provides attackers with a powerful foothold for further compromise within the TeamCity environment. Successful exploitation can enable attackers to access sensitive build configurations, view private source code repositories, manipulate build processes, and potentially gain access to underlying infrastructure. The vulnerability affects the core administrative functionality of TeamCity, which typically includes project management, user access control, build agent configuration, and system settings. An attacker could use the stored XSS to escalate privileges, modify authentication settings, or redirect administrators to phishing sites designed to harvest credentials. The persistent nature of the vulnerability means that once exploited, the malicious payload continues to execute whenever administrators access the affected pages, potentially allowing for long-term surveillance or continued unauthorized access. This vulnerability directly impacts the integrity and confidentiality of the continuous integration/continuous deployment pipeline, as it can compromise the entire build infrastructure and potentially expose sensitive development artifacts.
Organizations affected by CVE-2020-15830 should immediately upgrade to TeamCity version 2019.2.3 or later, which includes proper input validation and output sanitization measures. Additionally, administrators should implement network segmentation to limit access to the TeamCity administration interface, enforce strict access controls, and monitor for suspicious activity in the application logs. Security teams should conduct thorough audits of all administrative accounts and consider implementing multi-factor authentication to reduce the risk of unauthorized access. The vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws, and represents a classic example of how insufficient input validation can lead to persistent security weaknesses. From an ATT&CK framework perspective, this vulnerability maps to techniques such as T1059.007 (Command and Scripting Interpreter: JavaScript) and T1566 (Phishing) as attackers can leverage the stored XSS to execute malicious scripts and potentially harvest credentials. Organizations should also consider implementing web application firewalls and content security policies to provide additional protection against similar vulnerabilities in the future. Regular security assessments of web applications and proactive patch management are essential to prevent exploitation of such persistent security flaws.