---
title: "CVE-2026-63077: JetBrains TeamCity Deserialization of Untrusted Data Vulnerability"
url: https://erroneo.us/security/cve/CVE-2026-63077/
description: "CVE-2026-63077 (JetBrains TeamCity): Exploited in the wild (CISA KEV). In JetBrains TeamCity before 2026.1.3, 2025.11.7 unauthenticated remote code…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-07-27
date_modified: 2026-10-21
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-63077"
kev: true
cvss: 9.8
epss: 0.8957
license: All rights reserved. Quote with attribution and a link.
---

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

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run JetBrains TeamCity. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-08-05, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-08-08 ; treat that as the outer limit, not the target. CISA also lists it as known to be used in ransomware campaigns .
- EPSS 89.6% , percentile 99.8: FIRST’s model estimates a 89.6% chance of exploitation activity in the next 30 days, higher than 99.8% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Editorial verdict: Act now. TeamCity CVE-2026-63077: Unauthenticated RCE, Exploited — Any self-hosted TeamCity server below 2025.11.7 or 2026.1.3 that an attacker can reach over HTTP(S) can be taken over without credentials, and ransomware crews are using it; patch or apply the security patch plugin today, then check for intrusions.

## What it is

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

## Affected products (CVE record)

- JetBrains TeamCity: < 2026.1.3, 2025.11.7

## Severity

- JetBrains CVSS 3.1: 9.8 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`

## Exploitation

- CISA KEV: added 2026-08-05; federal due date 2026-08-08. Known ransomware use: Known.
- 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 SSVC assessment: exploitation active , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 89.57% probability of exploitation activity in the next 30 days; percentile 99.8.

## Sources

- [Listed in CISA KEV notes (blog.jetbrains.com)](https://blog.jetbrains.com/teamcity/2026/07/cve-2026-63077/)
- [Listed in CISA KEV notes (jetbrains.com)](https://www.jetbrains.com/privacy-security/issues-fixed/)
- [CVE.org record CVE-2026-63077](https://www.cve.org/CVERecord?id=CVE-2026-63077)
- [NVD entry CVE-2026-63077](https://nvd.nist.gov/vuln/detail/CVE-2026-63077)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-63077)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk)

---
Source page: https://erroneo.us/security/cve/CVE-2026-63077/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt