A recent security warning revealed that a small misconfiguration in AWS CodeBuild could have led to widespread compromises of key AWS GitHub repositories. Researchers from Wiz uncovered a subtle flaw that could have allowed hackers to take control of essential AWS projects, including the popular JavaScript SDK used in the AWS Console. Fortunately, AWS responded quickly to fix the issue before it could be exploited at scale.

The Vulnerability Explained

The problem originated from a minor flaw in how AWS CodeBuild’s continuous integration (CI) pipelines handled build triggers. Specifically, a missing two characters in a regular expression (regex) filter allowed attackers to bypass security checks. This filter is responsible for scanning logs for secrets like passwords or tokens and hiding them to prevent leaks. Because of the typo, attackers could manipulate the build process without proper authorization, gaining access to privileged credentials stored in the environment.

This oversight meant that an attacker could potentially take over repositories associated with AWS projects, especially those containing critical libraries like the AWS JavaScript SDK. Such a breach could have resulted in malicious code being injected into widely used AWS components, creating a serious supply chain security risk.

Discovery and Response

The issue was discovered last August during an attempted attack on the Amazon Q VS Code extension. An attacker exploited a misconfigured CodeBuild project to infiltrate the extension’s GitHub repository. They managed to inject malicious code into the main branch, which was then included in a released version that users downloaded. Although the attack was ultimately thwarted due to a typo in the payload, it demonstrated how a small misconfiguration could have catastrophic consequences.

Wiz researchers quickly identified the core flaw as an unanchored regex that allowed threat actors to bypass security checks. They promptly notified AWS, which responded within 48 hours by patching the vulnerability. AWS also implemented additional security measures, including hardening build processes that handle sensitive tokens or credentials in memory.

In addition to fixing the immediate bug, AWS audited all related public build environments to ensure no similar issues remained. They reviewed logs from all relevant repositories and CloudTrail logs, confirming that no malicious activity had occurred due to this flaw. AWS assured users that there was no impact on customer data or the integrity of its services.

Lessons and Best Practices

This incident highlights how a tiny error, like a missing character in a regex, can open the door to serious security risks. It underscores the importance of rigorous testing and review of automation scripts and security filters used in development pipelines. Developers are advised to follow best practices when using AWS CodeBuild, especially around handling secrets and build triggers.

While AWS responded swiftly, the event serves as a reminder that supply chain security remains a critical concern. Small flaws can lead to big problems, especially when they exist in shared or open-source projects. Both cloud providers and developers need to stay vigilant and regularly audit their build and deployment systems to prevent similar vulnerabilities in the future.

Overall, this case demonstrates that even trusted cloud services require continuous scrutiny, and that quick action can prevent potential disasters. It also reinforces the need for meticulous security procedures in automated workflows to protect the entire software supply chain from malicious actors.

Inspired by

• https://www.infoworld.com/article/4117662/possible-software-supply-chain-attack-through-aws-codebuild-service-blunted.html

Sources

• wiz.io