CISA Warns of TeamCity RCE Vulnerability Actively Exploited in Attacks

CISA has warned that CVE-2026-63077, an unauthenticated deserialization RCE in JetBrains TeamCity On‑Premises, is being actively exploited; JetBrains published fixes (2025.11.7 and 2026.1.3) and CISA added the issue to its Known Exploited Vulnerabilities catalog with a remediation deadline. The report highlights severe supply‑chain risk from compromised build servers, recommends urgent patching or applying the vendor security plugin as a temporary measure, restricting access, reviewing logs and builds for signs of compromise, rotating secrets, and preserving forensic evidence.