Hackers exploiting critical software flaw right now.

Your company's software build process might be at risk if it uses a popular tool called TeamCity.

Here's the lowdown: The U.S. Cybersecurity and Infrastructure Security Agency (CISA), a government group that helps keep America's internet safe, recently put out a warning. They said that a serious security hole in JetBrains TeamCity, a program many companies use to manage how they build and release software, is being actively attacked by malicious actors. This isn't just a theoretical problem; bad guys are already using it.

The specific problem, known as CVE-2026-63077, is a "deserialization of untrusted data" flaw. Think of it like a recipe. When a computer program "serializes" data, it's like writing down a complex recipe in a compact form to send it somewhere else. "Deserialization" is when the computer at the other end reads that compact recipe and reconstructs the original dish. This flaw means that if a bad actor gives TeamCity a tampered, "untrusted" recipe, TeamCity might follow those instructions and do something it shouldn't, like giving the attacker full control.

This particular flaw has a scary rating of 9.8 out of 10 on the CVSS scale, which is basically a danger meter for security vulnerabilities. What makes it especially dangerous is that an attacker doesn't need a username or password to exploit it; they just need to be able to reach the TeamCity server over the internet. This could allow them to run their own code on the server, potentially taking over the entire system that builds and releases a company's software.

This isn't the first time TeamCity has been in the news for security issues. Earlier this year, other critical vulnerabilities in TeamCity were also exploited, highlighting a recurring pattern where tools central to software development become targets. These "supply chain" attacks, where vulnerabilities in development tools lead to broader security problems for companies, are a growing concern across the tech landscape.

If your organization uses on-premise TeamCity, meaning the software runs on your own company's servers rather than through a cloud service, it's crucial to act immediately. JetBrains has already released a patch, which is like a software update that fixes the problem. Make sure your IT team has applied this update to all your TeamCity servers without delay.

Applying the latest security updates is essential to protect your company's software development from active threats.