CVE-2026-75046 in YouTrack
Summary
by MITRE • 08/17/2026
In JetBrains YouTrack before 2026.2.18112 an authenticated user could enumerate accounts via the users search endpoint
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Analysis
by VulDB Data Team • 08/17/2026
The vulnerability identified in JetBrains YouTrack prior to version 2026.2.18112 represents a significant information disclosure flaw within the application's user management subsystem. Specifically, this issue resides in the API endpoint responsible for searching and listing user accounts. While authentication is required to access most administrative or project-specific features in YouTrack, the search functionality was implemented with insufficient input validation and output filtering mechanisms. This architectural oversight allows an authenticated attacker who possesses valid credentials for any standard user account to exploit the users search interface to enumerate existing usernames within the system. The flaw does not require elevated privileges such as administrator access, which significantly lowers the barrier to entry for exploitation by malicious insiders or external attackers who have compromised a low-privilege account through phishing or credential stuffing attacks.
From a technical perspective, this vulnerability is classified under CWE-203: Observable Discrepancy and CWE-200: Exposure of Sensitive Information to an Unauthorized Actor. The core issue stems from the API returning detailed user information based on partial string matches without implementing rate limiting, strict access control checks for enumeration-specific endpoints, or consistent error responses that would prevent timing attacks or existence verification. When a query is submitted against this endpoint, the system returns results indicating whether specific usernames exist in the database, even if those users do not have permission to view each other's profiles. This behavior effectively turns the search feature into an account enumeration tool, allowing attackers to build a comprehensive list of valid user accounts within the organization's YouTrack instance.
The operational impact of this vulnerability is primarily centered on facilitating further attacks rather than causing immediate data leakage or system compromise in itself. By successfully enumerating valid usernames, an attacker gains valuable intelligence about the target environment. This information can be leveraged to conduct targeted phishing campaigns, such as spear-phishing emails that appear more credible because they address specific employees by name. Furthermore, knowing which accounts exist allows attackers to perform credential stuffing attacks with higher accuracy, focusing their efforts on known valid usernames rather than guessing random ones. In environments where password policies are weak or reused across services, this enumeration can serve as the initial foothold for a broader compromise of corporate infrastructure.
This vulnerability aligns with several tactics and techniques within the MITRE ATT&CK framework. It directly supports the Reconnaissance phase under T1589: Gather Victim Identity Information, specifically through credential guessing or brute force methodologies where valid accounts are identified prior to attack execution. Additionally, it relates to T1078: Valid Accounts, as the attacker utilizes legitimate credentials to access system resources for unauthorized purposes. The ability to map out user identities also aids in lateral movement planning and privilege escalation strategies by identifying high-value targets such as administrators or developers with elevated permissions within the project management tool.
To mitigate this risk, organizations running versions of YouTrack prior to 2026.2.18112 must apply the vendor-provided patch immediately upon upgrade. JetBrains has addressed the underlying code logic that permitted unrestricted enumeration through the search endpoint in this release. Until the update is applied, administrators should consider implementing network-level controls such as Web Application Firewalls (WAF) to detect and block abnormal patterns of user enumeration requests. Rate limiting on the users search API can also help mitigate automated scanning tools by throttling excessive queries from a single source IP address or session token. Additionally, enforcing strict multi-factor authentication across all accounts reduces the likelihood that an enumerated username will lead to successful unauthorized access via password-based attacks. Regular audits of account permissions and ensuring least-privilege principles are applied to user roles can further reduce the attack surface associated with this vulnerability.