Description

In JetBrains YouTrack before 2026.2.18634 iP spoofing via HTTP headers allowed forged Bitbucket webhooks

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "3.3",
  "pubDate": "2026-09-07T17:17:26.723Z",
  "pubdate": "2026-09-07T17:17:26.723Z",
  "executiveSummary": "This vulnerability involves an IP spoofing flaw within JetBrains YouTrack versions prior to 2026.2.18634, specifically affecting the processing of Bitbucket webhooks.\nThe vulnerability allows an unauthenticated attacker to manipulate HTTP headers to bypass source IP verification mechanisms.\nBy successfully spoofing the expected origin IP address, an attacker can forge malicious Bitbucket webhooks, causing the YouTrack instance to process unauthorized requests.\nThe primary risk implications include the potential for unauthorized integration events, data manipulation, or the triggering of automated workflows within the affected YouTrack environment.\nExploitation does not require prior authentication, as the vulnerability resides in the network-level validation logic of the incoming webhook ingestion point.\nSuccessful exploitation requires the attacker to be able to reach the YouTrack instance via the network and craft specific HTTP request headers to simulate the trusted Bitbucket communication pattern.",
  "technicalDetails": "The root cause of this vulnerability lies in an improper implementation of source validation for incoming HTTP requests sent by Bitbucket integrations. The application relies on inspectable HTTP headers (often those intended for proxy identification, such as X-Forwarded-For) to determine the legitimacy of the request origin rather than enforcing strict network-layer source verification or utilizing mandatory cryptographic signature validation.\nIn a standard deployment, YouTrack validates Bitbucket webhooks to ensure that incoming payloads originate from trusted Bitbucket infrastructure. By manipulating the HTTP headers, an attacker can present a forged source IP address that the application incorrectly identifies as belonging to a trusted Bitbucket server. This bypasses the security controls designed to restrict webhook processing to authorized sources only.\nThe attack flow proceeds as follows: First, the attacker identifies the publicly reachable endpoint used by YouTrack to receive Bitbucket webhooks. Second, the attacker crafts an HTTP POST request, injecting specific headers that the vulnerable component uses for IP identification. Third, the attacker populates the request body with a malicious payload formatted to mirror legitimate Bitbucket webhook events. Finally, the YouTrack instance processes the forged request, executing associated internal logic—such as updating issue statuses, adding comments, or triggering CI/CD pipelines—as if the event were authenticated and legitimate.\nThis vulnerability is present in all JetBrains YouTrack versions prior to 2026.2.18634. Because the mechanism relies on the header-based trust model, the application remains susceptible to spoofing regardless of whether the incoming request is over HTTP or HTTPS, provided the header processing logic is reached. The impact is significant because it allows attackers to influence the state of the issue tracking system and potentially chain this access to execute further actions depending on the configured project automation rules.\nPost-exploitation, the attacker can effectively masquerade as the Bitbucket integration, potentially leading to unauthorized workflow state transitions or the injection of malicious data into tracked tickets, which may subsequently be viewed or executed by other users and systems integrated with YouTrack."
}