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CVE-2026-100255 – Administrator Account Takeover via Password Reset – JetBrains TeamCity before 2026

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Summary

CVE-2026-100255 is a high-severity vulnerability in JetBrains TeamCity that allows administrator account takeover through the server’s password reset functionality. The flaw is classified under CWE-1289 (Improper Validation of Specified Quantity in Input) and carries a CVSS v3.1 base score of 8.1. It affects all TeamCity versions prior to the vendor’s fixed releases and can be exploited remotely over the network, though the attack requires high complexity.

Technical details

  • Root cause: Improper validation of a specified quantity in input during the password reset workflow (CWE-1289), which enables an attacker to manipulate the reset process to gain control of an administrator account.
  • Trigger conditions: An attacker interacts with the TeamCity password reset feature; no prior privileges or user interaction from the victim are required, but the attack path has high complexity (AC:H).
  • Attack vector: Network-based (AV:N) — exploitable remotely against an internet-exposed TeamCity server without authentication (PR:N).
  • Impact: Successful exploitation results in full administrator account takeover, with high impact to confidentiality, integrity, and availability (C:H/I:H/A:H) of the TeamCity instance and, by extension, the CI/CD pipelines and connected systems it manages.

Affected software

  • JetBrains TeamCity: all versions prior to 2026.2
  • JetBrains TeamCity: all versions prior to 2026.1.4
  • JetBrains TeamCity: all versions prior to 2025.11.8

Severity

  • CVSS v3.1 Base Score: 8.1 (High)
  • Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Upgrade JetBrains TeamCity to version 2026.2, 2026.1.4, 2025.11.8, or later, which contain the fix for this issue.
  • If immediate patching is not possible: Restrict network access to the TeamCity server’s administrative and password reset endpoints to trusted networks or VPN only, monitor administrator account activity and password reset requests for anomalies, and enforce multi-factor authentication on administrator accounts where supported.

References

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