Unauthenticated Deserialization RCE in JetBrains TeamCity On-Premises
CISA: JetBrains TeamCity Deserialization of Untrusted Data Vulnerability
CVSS 3.1
9.8critical
EPSS
87%p100
Published
()
KEV added
AI analysis
CVE-2026-63077 is a critical (CVSS 9.8) unauthenticated remote code execution vulnerability in JetBrains TeamCity, caused by deserialization of untrusted data (CWE-502) in the agent polling protocol. An attacker with network access to the TeamCity server, but no credentials of any kind, can send maliciously crafted serialized input to the agent polling endpoint and execute arbitrary code on the server. Successful exploitation yields full server takeover, exposing source code, build logs, stored secrets and credentials, and providing a pivot point into build agents and connected infrastructure; related headlines describe a real breach in which AWS credentials were extracted from an unpatched TeamCity instance. Organizations running TeamCity On-Premises in versions prior to the fixes (2025.11.7 or 2026.1.3, depending on branch) are affected, while the JetBrains-hosted cloud service is not indicated as impacted. Exploitation is confirmed in the wild: CISA added the flaw to the Known Exploited Vulnerabilities catalog on 2026-08-05, EPSS is 86.5% (100th percentile), and no public PoC is known, meaning defenders cannot rely on public scanners alone and should assume sophisticated attackers are targeting exposed servers.
What to do: Upgrade immediately to TeamCity 2025.11.7 or 2026.1.3, whichever branch you run; because the flaw is pre-authentication, also hunt for signs of compromise (unexpected builds or agents, new or modified admin users, altered build configurations, and leaked stored credentials/secrets) per vendor guidance, and restrict internet exposure of the TeamCity server until patched. Federal agencies must apply vendor mitigations or discontinue use per CISA BOD 26-04 and the KEV required action, including the Forensics Triage Requirements.
Affected
JetBrains TeamCity On-Premises
all versions before 2025.11.7 (2025.11 branch) and before 2026.1.3 (2026.1 branch)
Estimated exposure
largetens of thousands of internet-exposed TeamCity on-premises servers (order of magnitude 10k-100k); total on-premises installs likely higher — TeamCity is one of the most widely deployed self-hosted CI/CD servers, and public internet-wide scans have historically shown TeamCity instances in the tens of thousands, with exploitation risk concentrated on servers whose agent-polling…
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description
In JetBrains TeamCity before 2026.1.3, 2025.11.7 unauthenticated remote code execution was possible via the agent polling protocol
CISA Known Exploited Vulnerability
Affected
JetBrains TeamCity
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.
Unknown attackers exploited critical TeamCity flaw CVE-2026-63077 to breach JetBrains Cadence, stealing a 2024 backup, user data, and AWS credentials; rotation urged.
JetBrains disclosed that threat actors exploited CVE-2026-63077 (CVSS 9.8), a TeamCity deserialization vulnerability added to CISA's KEV catalog on August 5, 2026, to breach its Cadence cloud computing service, with the intrusion running August 8-24, 2026. Confirmed access includes personal data (usernames, names, emails, login timestamps, IPs), a full 2024 Cadence server backup containing credentials and configuration, multiple AWS IAM users and secrets, files in JetBrains S3 buckets, and possibly PyCharm-synchronized source code. The compromised api.cadence.jetbrains.com server has been taken offline and all Cadence plugin access tokens invalidated. JetBrains urges users to immediately revoke or rotate all credentials used with Cadence and treat all executions, inputs, and outputs as potentially untrusted.
JetBrains fixed critical unauthenticated RCE CVE-2026-63077 in TeamCity On-Premises; update to 2025.11.7 or 2026.1.3.
JetBrains disclosed CVE-2026-63077, a critical unauthenticated remote code execution vulnerability affecting all TeamCity On-Premises versions. An attacker with HTTP(S) access can bypass authentication checks via the TeamCity agent polling protocol and execute arbitrary operating system commands with the privileges of the server process. Fixes are available in versions 2025.11.7 and 2026.1.3, plus a security patch plugin for TeamCity 2017.1+. JetBrains states there is no evidence of active exploitation at disclosure time, and TeamCity Cloud is already mitigated.
On July 27, 2026, JetBrains published a security advisory for CVE-2026-63077, a critical unauthenticated vulnerability affecting all versions of TeamCity On-Premises. The issue is classified as deserialization of untrusted data and has a CVSS score of 9.8.
Metasploit adds 16 modules including 10 exploits, five covering CISA KEV vulnerabilities in Cisco, SonicWall, PaperCut, JetBrains and Langflow.
Rapid7's weekly Metasploit update ships 16 new modules, 10 of them exploit modules, with five targeting CISA KEV entries. New exploits cover Cisco Secure Firewall Management Center auth bypass (CVE-2026-20079), a SonicWall SMA1000 SSRF-to-root RCE chain (CVE-2026-83548/CVE-2026-83549), JetBrains TeamCity deserialization RCE (CVE-2026-63077), PaperCut NG/MF chain (CVE-2026-81578/CVE-2026-82078), and Langflow authenticated RCE (CVE-2026-19295). The SonicWall and PaperCut chains were reported as actively exploited zero-days, and a new ESC8 relay module exploits CVE-2026-20929 against AD CS Web Enrollment.