This Critical Flaw in TeamCity Lets Attackers Run Commands Without Logging In

Emily Davis · 2026-07-28

JetBrains just dropped an urgent security alert for anyone running their own TeamCity server. If you're using the on-premise version, you need to pay attention because there's a nasty vulnerability that could let attackers take full control of your system without even needing a password. This isn't a minor bug. We're talking about a critical flaw that lets someone run any OS command on your server remotely. And the scariest part? They don't need to log in first. It's like leaving the front door wide open with a sign that says "come on in." ### The Vulnerability in Plain English The issue has been assigned CVE-2026-63077, and it carries a CVSS score of 9.8 out of 10. That's about as bad as it gets. For context, most critical vulnerabilities fall in the 9.0 to 10.0 range, so this one is right up there with the worst of them. What does this mean for you? If an attacker exploits this flaw, they can: - Execute arbitrary commands on your TeamCity server - Install malware or backdoors - Steal sensitive data like source code or credentials - Use your server as a launchpad to attack other systems on your network The vulnerability affects all versions of TeamCity On-Premises. That means if you're running any version before 2025.11.7 or 2026.1.3, you're exposed. ### Who Should Be Worried? If you're a developer, DevOps engineer, or IT administrator using TeamCity to manage your builds and deployments, this is your problem. TeamCity is a popular CI/CD tool used by thousands of organizations worldwide, from small startups to Fortune 500 companies. The good news? TeamCity Cloud instances have already been patched. So if you're using the cloud version, you're safe. But if you're running TeamCity on your own servers, you need to act now. ### What You Need to Do Right Now JetBrains has released patches in versions 2025.11.7 and 2026.1.3. The fix is straightforward: update to one of these versions immediately. Don't wait. Don't put it off until next week. This is the kind of vulnerability that attackers are actively scanning for. Here's your action plan: - Check your current TeamCity version right now - If you're on an older version, schedule the update for today - After updating, verify that the patch was applied correctly - Review your server logs for any suspicious activity ### Why This Matters for Antidetect Browser Users You might be wondering what a TeamCity vulnerability has to do with antidetect browsers. Here's the connection: if you're managing multiple online identities or running a business that relies on digital privacy, your infrastructure needs to be rock solid. A compromised CI/CD server can lead to leaked credentials, stolen session data, or worse. An antidetect browser helps you maintain separate digital fingerprints for different accounts or projects. But if your build server gets compromised, an attacker could potentially access your deployment scripts, environment variables, or even your source code. That's a direct threat to your operational security. Think of it this way: your antidetect browser is like a secure vault for your online identities. But if someone breaks into your server room, they can still get to the vault. That's why keeping all your software up to date is just as important as using the right privacy tools. ### The Bottom Line Security is a chain, and every link matters. A vulnerability like this one is a reminder that we can't afford to be complacent. Whether you're running TeamCity or any other critical infrastructure, staying on top of patches is non-negotiable. JetBrains has done their part by releasing a fix. Now it's up to you to apply it. Don't let this one slide. Your systems, your data, and your peace of mind depend on it.