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Actively exploitedKnown ransomware use

CVE-2024-27198 JetBrains TeamCity Authentication Bypass Vulnerability

JetBrains TeamCity contains an authentication bypass vulnerability that allows an attacker to perform admin actions.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch nowCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 7 Mar 2024.
  • CISA lists it as known to be used in ransomware campaigns.
  • Rated Critical severity (CVSS 9.8, scored by Vendor).
  • This product type is often exposed to the internet, which is where attackers scan for it first.
  • Named in Cybergen threat actor reporting: Medusa.
  • It has been in the catalogue for 974 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

In JetBrains TeamCity before 2023.11.4 authentication bypass allowing to perform admin actions was possible

Affected Versions

ProductVersions
JetBrains TeamCitybefore 2023.11.4

From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for JetBrains TeamCity. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated critical, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 28 Mar 2024 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

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CVE-2026-63077 · RansomwareJetBrains TeamCity Deserialization of Untrusted Data VulnerabilityAdded 5 Aug 2026CVE-2024-27199 · RansomwareJetBrains TeamCity Relative Path Traversal VulnerabilityAdded 20 Apr 2026CVE-2023-42793 · RansomwareJetBrains TeamCity Authentication Bypass VulnerabilityAdded 4 Oct 2023

All 4 exploited JetBrains vulnerabilities

Not Sure If You Are Exposed?

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2024-27198
  3. CVE record: CVE-2024-27198
  4. FIRST EPSS
  5. jetbrains.com/help/teamcity/teamcity-2023-11-4-release-notes.html
  6. blog.jetbrains.com/teamcity/2024/03/additional-critical-security-issues-affecting-teamcity-on-premis
  7. jetbrains.com/privacy-security/issues-fixed/
  8. darkreading.com/cyberattacks-data-breaches/jetbrains-teamcity-mass-exploitation-underway-rogue-accou