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CVE-2026-100277 – Account Takeover via Notification Signature Replay – JetBrains YouTrack before 202

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Summary

CVE-2026-100277 is an incorrect authorization vulnerability (CWE-863) in JetBrains YouTrack that allows an attacker to take over user accounts by replaying a notification signature. The issue affects all versions of YouTrack prior to 2026.2.19197 and carries a High severity CVSS v3.1 score of 8.9.

Technical details

  • Root cause: YouTrack’s notification mechanism generates a signature that is not adequately protected against reuse, allowing incorrect authorization (CWE-863) when that signature is replayed.
  • Trigger condition: An attacker who obtains or captures a valid notification signature can replay it to be authenticated as the targeted user, without needing valid credentials.
  • Attack vector: Network — exploitable remotely against internet-exposed YouTrack instances; no privileges or user interaction are required, though attack complexity is High.
  • Impact: Successful exploitation results in account takeover, with high impact to confidentiality and integrity and low impact to availability. The CVSS vector reflects a scope change (S:C), indicating the impact extends beyond the vulnerable component itself.

Affected software

  • JetBrains YouTrack — all versions prior to 2026.2.19197

Severity

  • CVSS v3.1 Base Score: 8.9 (High)
  • Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L

Mitigation and recommended actions

  • Immediate: Upgrade JetBrains YouTrack to version 2026.2.19197 or later, which resolves this vulnerability.
  • If immediate patching is not possible: Restrict network exposure of YouTrack instances (e.g., limit access to trusted networks or VPN), monitor for anomalous notification-related traffic, and review account activity for signs of unauthorized access until the upgrade can be applied.

References

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