CVE-2026-63077 — Teamcity
CRITICALCVE-2026-63077 is a critical-severity (CVSS 9.8) Deserialization of Untrusted Data vulnerability in jetbrains teamcity. It is in CISA's Known Exploited Vulnerabilities catalog (added 2026-08-05) and has been used in ransomware campaigns — treat it as actively exploited and patch now. A fix is available — see the affected versions and patch details below.
In JetBrains TeamCity before 2026.1.3, 2025.11.7 unauthenticated remote code execution was possible via the agent polling protocol
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2026-08-05 — including use in ransomware campaigns. Federal agencies were required to remediate by 2026-08-08.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2026-63077.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-63077 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).
Where this sits among everything scored
Of 397,508 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.
Description
In JetBrains TeamCity before 2026.1.3, 2025.11.7 unauthenticated remote code execution was possible via the agent polling protocol
Affected Products
teamcityjetbrainsResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Vendor / applianceDetect
Inventory every jetbrains teamcity deployment and check each version against the affected-products list above.
Fix
Apply the jetbrains teamcity security patch or hotfix for CVE-2026-63077 on the affected version, following the vendor advisory for your exact build.
Workarounds
Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
How to detect CVE-2026-63077
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2026-63077 -u https://target- Template
- JetBrains TeamCity < 2026.1.3, 2025.11.7 - Remote Code Execution
- Severity
- critical
- Impact
- Unauthenticated remote attackers can execute arbitrary code with the privileges of the TeamCity server process.
- Remediation
- Upgrade to TeamCity 2026.1.3, 2025.11.7 or later.
Template by ProjectDiscovery nuclei-templates (0x_Akoko, pdteam), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2026-63077 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.