JetBrains TeamCity: Sandbox escape in versioned settings Kotlin DSL
Summary
A sandbox escape in the versioned settings Kotlin DSL of JetBrains TeamCity allows an attacker to execute code on the TeamCity server. The CVSS score is 8.8 (high). The attacker needs a low-privileged account and network access to TeamCity; no user interaction is required.
Affected
- JetBrains TeamCity before 2026.2
- JetBrains TeamCity 2026.1.x before 2026.1.4 (per Tenable reading)
- Exact per-branch range: verify on the JetBrains advisory page. The CVE record lists versions before 2026.2, 2026.1.4 and 2025.11.8.
Fixed in
- Upgrade to 2026.2 or later (recommended)
- Alternatively, 2026.1.4 for branch 2026.1 and 2025.11.8 for branch 2025.11 (verify on the JetBrains page)
Workaround
- No vendor workaround for this CVE was found.
- Limit who can edit versioned settings and Kotlin DSL.
- Do not expose the TeamCity web interface to the internet without a VPN or equivalent layer.
Exploitation
- No known exploitation in the wild.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- No public proof of concept found; this is absence of evidence, not confirmation.
Our recommendation
- Inventory all TeamCity servers and their exact versions, including test instances.
- Upgrade to the fixed build for your branch, ideally 2026.2 or later, and confirm the target on the JetBrains page.
- Remove direct internet exposure of TeamCity.
- Limit who can change versioned settings and review recent build configuration changes.
- Prioritise CVE-2026-63077 (unauthenticated RCE, fixed in 2025.11.7 and 2026.1.3) if your servers run older builds.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- JetBrains: Fixed security issues www.jetbrains.com
- OpenCVE: CVE-2026-100253 app.opencve.io
- Tenable Nessus plugin 362481 www.tenable.com
- Vulners Nessus plugin (TeamCity 2026.2 / 2026.1.4 / 2025.11.8) vulners.com
- JetBrains blog: CVE-2026-63077 blog.jetbrains.com
- JetBrains: Kotlin DSL execution mode (SANDBOX) www.jetbrains.com
- HOL Guard: CISA ADP VulnRichment for CVE-2026-100253 hol.org
- Help Net Security: TeamCity CVE-2026-63077 fixed www.helpnetsecurity.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 31 Oct 2026, 23:06.
Original description (NVD)
In JetBrains TeamCity before 2026.2, 2026.1.4, 2025.11.8 sandbox escape leading to code execution was possible via the versioned settings Kotlin DSL
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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