DEF CON 32 - Your CI CD Pipeline Is Vulnerable, But It's Not Your Fault - Elad Pticha, Oreen Livni

[GitHub Actions pipelines are vulnerable to command injection due to untrusted user inputs and third-party custom actions, even when the pipeline itself appears secure. This vulnerability can lead to full repository compromise and exposure of sensitive credentials.]2:59

Key Takeaways:
• Command injection in GitHub Actions occurs when user-controlled inputs (e.g., issue titles) are directly used in commands without sanitization, allowing attackers to exfiltrate secrets 10:15-11:19.
• Custom actions introduce supply chain risks: vulnerable dependencies in third-party actions can be exploited to compromise entire pipelines, even if the user code is clean 14:55-15:31.
• The Bazel project, a Google-owned open-source tool, was found to have a critical command injection vulnerability in a custom action, enabling attackers to gain full repository access and exfiltrate secrets 19:17-21:47.

This attack demonstrates how insecure inputs and dependency chains can lead to widespread compromise, even in well-maintained projects. Organizations must enforce input validation, audit third-party actions, and follow the principle of least privilege in CI/CD workflows.

Sources:

• 2:59 Overview of GitHub Actions vulnerabilities and attack surface
• 10:15-11:19 Demonstration of command injection via user-controlled inputs
• 14:55-15:31 Explanation of custom action dependency risks
• 19:17-21:47 Discovery and exploitation of Bazel’s command injection vulnerability