CVE-2021-43202 in TeamCity
Summary
by MITRE • 11/30/2021
In JetBrains TeamCity before 2021.1.3, the X-Frame-Options header is missing in some cases.
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Analysis
by VulDB Data Team • 12/04/2021
The vulnerability identified as CVE-2021-43202 affects JetBrains TeamCity versions prior to 2021.1.3 and relates to the improper implementation of the X-Frame-Options HTTP response header. This header serves as a critical security mechanism designed to prevent clickjacking attacks by controlling whether a web page can be embedded within an iframe. The absence of this header in certain scenarios creates a significant security gap that adversaries can exploit to gain unauthorized access to sensitive information or perform malicious actions through iframe-based attacks.
The technical flaw manifests when the X-Frame-Options header is not consistently applied across all responses generated by the TeamCity application. This header typically takes one of three values: DENY, SAMEORIGIN, or ALLOW-FROM, each serving to control iframe embedding behavior. When missing, web applications become vulnerable to clickjacking attacks where malicious actors can overlay transparent or opaque elements over legitimate user interface components to trick users into performing unintended actions. This vulnerability directly maps to CWE-1021, which specifically addresses inadequate protection against clickjacking attacks, and aligns with ATT&CK technique T1211 where adversaries leverage web-based attacks to manipulate user interactions.
The operational impact of this vulnerability extends beyond simple information disclosure to encompass potential privilege escalation and unauthorized access to administrative functions within the TeamCity environment. Attackers can craft malicious web pages that embed the TeamCity interface within iframes, potentially capturing user credentials, manipulating build configurations, or executing unauthorized administrative commands. This risk is particularly elevated in environments where TeamCity serves as a central automation platform with extensive access to development infrastructure and sensitive code repositories.
Organizations using affected TeamCity versions should immediately implement the available patch updates to address this vulnerability. The remediation involves ensuring that the X-Frame-Options header is consistently applied to all HTTP responses, with appropriate values based on the application's security requirements. Security teams should also conduct comprehensive audits of their TeamCity configurations to verify proper header implementation across all endpoints and consider implementing additional security headers such as Content Security Policy to provide layered protection against similar vulnerabilities. The fix demonstrates the importance of maintaining consistent security headers across all web applications and aligns with industry best practices for defense in depth as outlined in NIST SP 800-53 and ISO 27001 frameworks.