CVE-2026-111094 is a deserialization flaw (CWE-502) in JetBrains TeamCity, scored 8.1 high. A whitelist bypass in the build messages protocol allows remote code execution. It affects versions before 2026.2, 2026.1.4 and 2025.11.8. Update to a fixed version on your release line.
What's affected
JetBrains TeamCity before 2026.2, before 2026.1.4 and before 2025.11.8, per the CVE record. The fixed versions are 2026.2, 2026.1.4 and 2025.11.8, each on its own release line.
The record gives few details. It says only that a whitelist bypass in the build messages protocol made remote code execution possible. JetBrains tracks the fix on its security issues page, so check that page for the entry and any extra guidance.
How to check if you're exposed
Check the version of your TeamCity server in the web interface, and note the release line (2025.11, 2026.1 or 2026.2). Compare it with the fixed versions above. Build agents connect to the server, so check the version of agents too if your upgrade process treats them separately.
Then look at who can reach the server and agents. List where the server is exposed, and whether agents connect over untrusted networks. Review the server audit log and agent logs for unusual build messages or unexpected agent behavior.
A build server is also a place where secrets live, so list the credentials that jobs can read.
You can also run the free in-browser dependency scan or browse the Gold directory to see where a package or product shows up in your stack.
What to do now
- Update TeamCity to 2026.2, 2026.1.4 or 2025.11.8, whichever matches your line, and make sure agents update with it.
- Read the JetBrains security issues page for guidance specific to this fix.
- Limit network access to the server and agents to the systems that need it.
- Review audit logs and recent build changes for unexpected activity.
- If you suspect abuse, rotate the secrets, tokens and deploy keys that the server can reach.
Why it matters
Deserialization takes bytes from a message and rebuilds objects from them. If the code accepts classes it should not, the message can cause code to run. The usual defense is a whitelist of allowed classes, and the record says this one could be bypassed. The class is CWE-502.
The score is 8.1 and not higher, which usually means conditions such as network position or complexity apply. Do not read that as low risk. A build server holds source code, signing keys and deploy credentials, so a code execution flaw there reaches the software supply chain.
The record does not flag this CVE as exploited in the wild and it is not a CISA Known Exploited Vulnerability.
Quick check
Do build agents need updating too?
Check the JetBrains guidance. Agents normally update from the server, but verify the version after the server upgrade.
Why does a CI flaw matter so much?
CI servers hold source, secrets and deploy rights, so code execution on one can lead to tampered builds.
Sources
Last reviewed: 19 October 2026.
