CVE-2026-100255 in TeamCity
Summary
by MITRE • 09/30/2026
In JetBrains TeamCity before 2026.2, 2026.1.4, 2025.11.8 administrator account takeover was possible via password reset
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Analysis
by VulDB Data Team • 09/30/2026
The vulnerability identified in JetBrains TeamCity versions prior to the specified patches represents a critical authentication bypass mechanism that allows an attacker to seize control of administrative accounts through improper handling of password reset procedures. This flaw stems from insufficient validation and state management within the application's identity verification workflow, specifically targeting the mechanisms used for resetting user credentials. In many web-based applications, password resets rely on tokens or temporary codes sent via email or generated internally to verify the requester's ownership of an account. However, in this instance, the implementation failed to adequately restrict who could initiate these reset requests or how those requests were processed by the server side logic.
From a technical perspective, the core issue lies in the lack of proper authorization checks during the password reset transaction. An attacker with access to any valid user account, potentially even a low-privileged one, can exploit this flaw to trigger a password change for an administrator account without possessing the original admin credentials or receiving the legitimate verification token intended for that specific high-level role. This suggests that the application does not sufficiently differentiate between standard users and administrators when processing reset requests, allowing lateral movement from a lower privilege level directly into a privileged administrative state. The absence of multi-factor authentication requirements during this critical step further exacerbates the risk, as it relies solely on knowledge-based or token-based verification which can be manipulated under certain conditions within the application's logic flow.
The operational impact of such a vulnerability is severe and potentially catastrophic for organizations relying on TeamCity for their continuous integration and deployment pipelines. An attacker who successfully executes this attack gains full administrative access to the build server environment. This level of control enables the execution of arbitrary code, modification of build configurations, theft of sensitive source code or credentials stored within project settings, and disruption of critical development workflows. Furthermore, because TeamCity often serves as a central hub for deployment artifacts and infrastructure automation scripts, compromising it can provide an attacker with a persistent foothold to pivot into other parts of the network, access production systems, or exfiltrate intellectual property on a massive scale. The ability to take over admin accounts without detection also undermines audit trails and security monitoring efforts, as actions performed by the compromised account appear legitimate within the system logs.
This vulnerability aligns with CWE-287, which describes Improper Authentication, specifically focusing on scenarios where authentication mechanisms are bypassed or manipulated through flawed logic rather than cryptographic weaknesses. It also relates to CWE-640, Weak Password Recovery Mechanisms for Administrators, highlighting the inadequacy of safeguards designed to protect high-value accounts during recovery processes. In terms of offensive security frameworks, this attack vector corresponds to MITRE ATT&CK technique T1078, Valid Accounts, where adversaries leverage legitimate credentials or account privileges to maintain access and escalate their permissions within a target environment. The exploitation path typically involves initial low-level access followed by privilege escalation through the flawed reset mechanism, fitting into broader campaigns aimed at establishing persistent administrative control over critical infrastructure components.
Mitigation strategies must prioritize immediate patching of all affected TeamCity instances to versions 2026.2 or later, as well as 2026.1.4 and 2025.11.8, which contain the necessary code corrections for these authentication flaws. Organizations should also enforce strict access controls by limiting who can initiate password resets for administrative accounts, ensuring that such actions require additional verification steps beyond standard user protocols. Implementing multi-factor authentication across all user levels, particularly for administrators and service accounts, adds a critical layer of defense against credential-based attacks. Regular security audits focusing on identity management workflows are essential to identify similar logic flaws in other enterprise applications. Additionally, monitoring logs for unusual patterns in password reset requests, such as high-frequency attempts or resets initiated from unexpected IP addresses, can help detect exploitation attempts before full account takeover occurs.