Description

In JetBrains YouTrack before 2026.2.18634 a crafted WebSocket message allowed read-only whiteboard users to modify canvas content

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "3.1",
  "pubDate": "2026-09-07T17:17:26.947Z",
  "pubdate": "2026-09-07T17:17:26.947Z",
  "executiveSummary": "A broken access control vulnerability exists in JetBrains YouTrack versions prior to 2026.2.18634, specifically within the whiteboard canvas component.\nThis vulnerability allows users with read-only permissions to perform unauthorized write operations, effectively bypassing existing authorization constraints.\nThe flaw resides in the handling of WebSocket communications, where the application fails to properly validate the authorization level of incoming messages intended for canvas modification.\nAn attacker possessing only read-only access to a specific whiteboard can leverage this flaw to alter, append, or delete content, thereby compromising the integrity of shared documentation and visual collaborative assets.\nThe risk implication is significant due to the potential for unauthorized data manipulation within collaborative environments. Exploitation does not require elevated administrative privileges, as the vulnerability is triggered through the standard WebSocket interface used by the application for real-time collaboration. By crafting specific, malformed, or unauthorized WebSocket messages, an attacker can coerce the server-side whiteboard service into committing changes that should be restricted based on the user's defined permission set.",
  "technicalDetails": "The vulnerability is rooted in an improper authorization check during the processing of WebSocket frames directed at the YouTrack whiteboard service. In the affected versions of YouTrack, the whiteboard functionality relies on a persistent WebSocket connection to synchronize canvas states in real-time across multiple clients.\nWhile the application enforces read-only state at the user-interface level for unauthorized users, the backend server-side implementation fails to perform an adequate secondary verification of the user's authorization level upon receipt of specific WebSocket opcodes or messages.\nThe attack flow begins with the establishment of a legitimate WebSocket connection by an authenticated user assigned 'read-only' whiteboard permissions. The attacker then inspects the structure of the WebSocket frames used to transmit canvas modifications (such as object insertion, deletion, or transformation commands).\nBy crafting a malicious payload that mimics the structure of valid modification requests—even if the attacker lacks the corresponding write-permissions—the client can inject unauthorized commands into the synchronization stream. Because the whiteboard component does not validate that the incoming command originated from a session authorized to mutate the document state, the server processes the payload as a legitimate modification.\nThis leads to a state synchronization discrepancy, where the server updates the master state of the whiteboard and propagates the unauthorized changes to all other connected clients. The vulnerable component is the server-side WebSocket message handler responsible for parsing canvas transaction objects.\nBecause the WebSocket protocol allows for asynchronous, bidirectional communication, the attacker can silently push updates without triggering common request-response security filters that might exist on standard HTTP endpoints. The post-exploitation impact includes the loss of document integrity, the ability for malicious actors to deface collaborative boards, and the potential for 'silent' modification of project data, which can lead to misinformation or the corruption of critical visual workflow documentation. The exploit is effective as long as the attacker has established an authenticated session with at least read-only access to the targeted whiteboard resource."
}