CISA Flags TeamCity CVE-2026-63077 RCE Flaw Under Active Exploitation in the Wild

A newly patched security flaw impacting on-premise versions of JetBrains TeamCity has come under active exploitation in the wild, according to the U.S. Cybersecurity and Infrastructure Security Agency (CISA). The vulnerability in question is CVE-2026-63077 (CVSS score: 9.8), a case of deserialization of untrusted data that could allow an unauthenticated attacker with access to a TeamCity server

Because the vulnerability was publicly disclosed with technical detail, the risk of exploitation increases sharply until a patch is applied across all affected systems.

Security teams should review their detection rules, keep threat-intelligence feeds current, and validate that incident-response runbooks are tested before an incident occurs.