CVE-2026-63077: JetBrains TeamCity Deserialization of Untrusted Data Vulnerability

In short

JetBrains TeamCity has a weakness classified as deserialization of untrusted data (CWE-502). CISA added it to its Known Exploited Vulnerabilities catalog on 2026-08-05. NVD lists CVSS 3.1 at 9.8 CRITICAL. CISA reports known ransomware campaign use.

What it is

“JetBrains TeamCity contains a deserialization of untrusted data vulnerability that could allow unauthenticated remote code execution via the agent polling protocol.” — CISA KEV, retrieved 2026-11-01

“In JetBrains TeamCity before 2026.1.3, 2025.11.7 unauthenticated remote code execution was possible via the agent polling protocol” — NVD, retrieved 2026-11-01

Who is affected

JetBrains TeamCity. NVD lists the following versions as affected:

• Versions before 2025.11.7
• Versions from 2026.1 inclusive, before 2026.1.3

Exploitation status

CISA KEV added: 2026-08-05. Known ransomware campaign use: Known (reported by CISA). Due date CISA set for US federal civilian agencies: 2026-08-08.

Scores

NVD CVSS 3.1: 9.8 CRITICAL; vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H; source [email protected].

EPSS by FIRST: 93.56%; percentile 99.84; score date 2026-10-31. EPSS estimates the probability of exploitation in the next 30 days.

CWE: CWE-502.

Timeline

CISA required action

“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.” — CISA KEV

What to do

• Confirm whether you run JetBrains TeamCity and which version.
• Apply the vendor update or mitigation in the advisory.
• Follow CISA’s required action.
• Review the vendor guidance on signs of compromise.
• Track the fix through completion.

References

• Vendor Advisory: https://www.jetbrains.com/privacy-security/issues-fixed/
• NVD detail
• CVE.org record
• CISA KEV catalog

Sources and dates

CISA Known Exploited Vulnerabilities Catalog, version 2026.10.30; retrieved 2026-11-01. CISA KEV data: CC0 1.0. No endorsement by CISA.

NVD retrieved: 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.

EPSS scores by FIRST; score date 2026-10-31.