CVE-2026-63077

JetBrains TeamCity Deserialization of Untrusted Data Vulnerability

Exploited in attacks Used by ransomware Critical 9.8 Attack chance: 94%

What it is

In JetBrains TeamCity before 2026.1.3, 2025.11.7 unauthenticated remote code execution was possible via the agent polling protocol

CISA: JetBrains TeamCity contains a deserialization of untrusted data vulnerability that could allow unauthenticated remote code execution via the agent polling protocol.

What to do

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Deadline for US federal agencies: August 8, 2026

Added to the CISA list: August 5, 2026
Published: July 27, 2026
Severity: Critical 9.8 CVSS 3.1
Chance of attacks in the next 30 days (EPSS): 94% in the top 0.2% of all known vulnerabilities
Weakness: CWE-502
More details: NVD · CVE.org · CISA

All references (1)

https://www.jetbrains.com/privacy-security/issues-fixed/

More exploited flaws from JetBrains

Added	Vulnerability	Product	Severity	Attack chance
Apr 20, 2026	Relative Path TraversalCVE-2024-27199used by ransomware	TeamCity	High 7.3	>99.9%
Mar 7, 2024	Authentication BypassCVE-2024-27198used by ransomware	TeamCity	Critical 9.8	99.9%
Oct 4, 2023	Authentication BypassCVE-2023-42793used by ransomware	TeamCity	Critical 9.8	>99.9%

All of them →

Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.