CVE-2025-52879 in TeamCity
Summary
by MITRE • 06/23/2025
In JetBrains TeamCity before 2025.03.3 reflected XSS in the NPM Registry integration was possible
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Analysis
by VulDB Data Team • 06/25/2025
The vulnerability identified as CVE-2025-52879 represents a reflected cross-site scripting flaw within JetBrains TeamCity's NPM Registry integration component. This security weakness affects versions prior to 2025.03.3 and specifically targets the handling of user-supplied input within the NPM registry functionality. The vulnerability arises from insufficient sanitization of input parameters that are reflected back to users without proper encoding or validation mechanisms. Attackers can exploit this flaw by crafting malicious payloads that are then executed in the context of other users' browsers who access the affected TeamCity instance.
The technical implementation of this vulnerability stems from the improper handling of NPM package metadata and registry responses within TeamCity's web interface. When TeamCity processes requests related to NPM package information, it fails to adequately sanitize or encode user-provided data before rendering it in web pages. This creates an environment where malicious input can be injected and subsequently executed as JavaScript code in the browser of authenticated users. The reflected nature of the vulnerability means that the malicious payload must be crafted specifically for each user session and delivered through a crafted URL or request parameter.
The operational impact of this vulnerability extends beyond simple script execution as it can enable attackers to perform various malicious activities within the context of authenticated TeamCity users. An attacker could potentially steal session cookies, perform unauthorized actions on behalf of users, or redirect victims to malicious websites. Given that TeamCity serves as a continuous integration and deployment platform, the exploitation of this vulnerability could compromise build processes, access sensitive project information, or potentially gain access to underlying infrastructure. The attack vector typically involves sending a specially crafted URL to a victim user who has access to the TeamCity instance, making this particularly dangerous in environments where multiple developers or administrators have access to the system.
The vulnerability aligns with CWE-79 which defines Cross-Site Scripting as a weakness where untrusted data is sent to a web browser without proper validation or encoding. This weakness is commonly exploited in web applications where user input is not properly sanitized before being rendered in web pages. From an ATT&CK framework perspective, this vulnerability maps to T1566.001 which covers Phishing with Social Engineering, as attackers would need to deliver malicious payloads through social engineering techniques to trick users into executing the malicious code. Additionally, the technique T1071.004 for Application Layer Protocol: DNS could be relevant if attackers attempt to use the compromised TeamCity instance to redirect users to malicious domains.
Mitigation strategies for CVE-2025-52879 primarily focus on updating to the patched version 2025.03.3 or later, which implements proper input sanitization and output encoding for NPM registry integration components. Organizations should also implement additional security measures such as network segmentation to limit access to TeamCity instances, regular security scanning of the application, and monitoring for suspicious activities in the registry integration functionality. Implementing Content Security Policy headers can provide additional protection against XSS attacks by restricting script execution in the browser context. Security teams should also conduct regular penetration testing and code reviews focusing on input validation and output encoding mechanisms within the TeamCity application, particularly in areas related to external registry integrations. Access controls should be reviewed to ensure that only authorized personnel have access to registry-related functionality, reducing the potential impact of successful exploitation attempts.