Exploited. On CISA's list since 2026-08-05, and used by ransomware.

JetBrains TeamCity Deserialization of Untrusted Data Vulnerability

CVE-2026-63077 · JetBrains TeamCity · Published 2026-07-27

How bad would it be?

9.8 out of 10

CVSS rates it critical: about as damaging as flaws get.

How likely is it to be used?

94%

Estimated chance of exploitation in the next 30 days, among the top 1% of all scored flaws (EPSS, 2026-10-29).

Is it already being used?

Yes

CISA has seen it exploited in real attacks. For US government agencies the fix is deadline passed 83 days ago (2026-08-08).

What CISA says 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.

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

What the flaw is

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

From the NVD.

Fixes and advisories

www.jetbrains.comVendor Advisory

Learn this

Explore this week’s weaknesses and all learning topics

Understand the kind of weakness behind this flaw. These resources teach the weakness, rather than reproduce this specific CVE. Follow the vendor's advice above to fix the affected product.

Insecure deserialization

Rebuilding objects from untrusted saved data can trigger unintended behaviour.

CWE-502 · CISA KEV; NVD record: cve@jetbrains.com

Reading and practice labs · Free account for labs. Basic HTTP knowledge; some labs use Burp Suite.

Explore the labs at PortSwigger Web Security Academy How it is prevented

CWE is a catalogue of weakness types. Labels come from the sources shown and can differ or change. Resource matches reviewed 16 October 2026.

On SentryFeed

No story in the last 14 days has mentioned it.

Exploited flaws from CISA's KEV catalogue. Chance of exploitation from EPSS by FIRST. Descriptions and scores from the NVD. This product uses the NVD API but is not endorsed or certified by the NVD.