CVE-2026-100259 in YouTrack
Summary
by MITRE • 09/30/2026
In JetBrains YouTrack before 2026.2.18991 improper access control on Gantt chart allowed edits by users with view-only access
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Analysis
by VulDB Data Team • 09/30/2026
The vulnerability identified in JetBrains YouTrack prior to version 2026.2.18991 represents a critical failure in the application's authorization logic, specifically within the module responsible for rendering and interacting with the Gantt chart interface. This flaw stems from an improper access control mechanism where the backend API endpoints handling updates to task data do not sufficiently validate the permissions of the requesting user against the specific resource being modified. While the front-end interface correctly restricts users with view-only roles from seeing edit buttons or interactive elements, the server-side validation fails to enforce these restrictions when direct HTTP requests are made to the underlying data modification endpoints. This discrepancy between client-side presentation and server-side enforcement is a classic example of relying on security through obscurity rather than implementing robust identity and access management controls at every layer of the application stack.
From a technical perspective, this vulnerability allows authenticated users who have been granted read-only permissions for specific projects or issue trackers to bypass these limitations by crafting malicious requests that target the Gantt chart update APIs. By manipulating parameters such as task IDs, status values, or date fields associated with the timeline view, an attacker can successfully push changes to the database without triggering any authorization errors. The lack of server-side verification means that the application trusts the client's assertion of user intent rather than independently verifying whether the current session possesses the necessary write privileges for the targeted entity. This architectural weakness effectively nullifies the intended role-based access control model, reducing the distinction between viewer and editor roles to a superficial UI constraint rather than a hard security boundary.
The operational impact of this vulnerability is significant in environments where strict data integrity and audit trails are required. Users with view-only access can inadvertently or maliciously alter task statuses, modify due dates, change assignees, or update descriptions within the Gantt chart context. This leads to a compromise of data integrity, as project timelines and resource allocations may be distorted without authorization. Furthermore, such unauthorized modifications can disrupt workflow processes, cause confusion among team members who rely on accurate status updates, and potentially lead to financial or scheduling losses if critical path tasks are altered. In regulated industries where audit logs must accurately reflect authorized changes, this vulnerability also poses a compliance risk by allowing untracked or improperly attributed edits that bypass standard change management protocols.
To mitigate this issue, organizations should immediately upgrade JetBrains YouTrack to version 2026.2.18991 or later, which contains the necessary patches to enforce proper access control checks on all API endpoints related to Gantt chart interactions. Until an upgrade is feasible, administrators can implement network-level controls such as web application firewalls that inspect request payloads for unauthorized modification attempts by users with restricted roles. Additionally, it is advisable to review and enhance server-side validation logic in custom integrations or plugins that interact with YouTrack data, ensuring that every write operation explicitly verifies the user's permissions against the target resource before processing the change. Regular security audits focusing on broken access control patterns can help identify similar vulnerabilities across other modules of the application.
This vulnerability is categorized under CWE-269, which addresses Improper Privilege Assignment, as it involves a failure to enforce proper roles and privileges for users performing actions that exceed their assigned permissions. In terms of offensive security frameworks, this flaw aligns with MITRE ATT&CK technique T1078, specifically the Valid Accounts subcategory, where an attacker leverages legitimate credentials but exploits insufficient authorization checks to perform unauthorized actions. The scenario also reflects aspects of CWE-639, Authorization Bypass Through User-Controlled Key, if the vulnerability allows manipulation of identifiers to access or modify resources outside one's scope, although in this specific case it is primarily a direct bypass of role-based restrictions on existing accessible resources. Addressing these types of flaws requires a shift from client-side validation reliance to strict server-side authorization checks for every state-changing operation within the application lifecycle.