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From YAML to Root: CI/CD Pipeline Attacks and Countermeasures
.ical
2025-10-24 –, Europe

As CI/CD pipelines become integral to modern software development through systems like Azure DevOps or GitHub Actions, and tools such as Terraform and Ansible, their compromise can have devastating effects, from infrastructure breaches to mass malware distribution.

Originally, CI/CD pipelines were managed and accessed only by a limited group of administrators or integration engineers. However, with the widespread adoption of Infrastructure as Code, it has become increasingly common for companies to open controlled access to their pipelines—sometimes even to external clients. This shift supports use cases such as self-service sandbox environments, client-controlled infrastructure provisioning, or dynamic testbed deployments in multi-tenant platforms. While these scenarios offer flexibility and scalability, they also introduce new risks and potential attack vectors, making it critical to rethink pipeline security under this broader exposure model.

In this talk, we will demonstrate how an attacker can exploit seemingly limited permissions—such as those of a standard contributor account—to fully compromise a CI/CD pipeline and the underlying infrastructure. By chaining misconfigurations, abusing legitimate features, and bypassing common restrictions, we’ll show how limited access can quickly escalate into full control.
In the second phase of the talk, we’ll look at the defensive side: how a company can effectively secure its pipelines in a context where access is no longer limited to internal teams.

Talk Description and Structure

The talk is divided into two main parts: an offensive demonstration and a defensive strategy session.

Part 1 – Offensive: From Contributor to Full Compromise

We will begin with a realistic demonstration of attack scenarios showing how a basic contributor-level account can be used to hijack a CI/CD pipeline, escape the provided use cases and fully compromise the infrastructure through Terraform integration. To reflect real-world conditions, common pipeline protections will be enabled—and bypassed. Key topics include:

  • Remote Code Execution via pipeline files:

    We’ll explore how attackers can achieve RCE through configuration file manipulation or config file poisoning, Terraform constructs (e.g., external data sources, malicious custom providers or modules, abuse of provisioners), and other legitimate pipeline features.

  • Bypassing restrictions:

    Techniques to bypass provider restrictions, function or module blacklists, and CI/CD step filters will be demonstrated, showing how misconfigurations or insufficient validation open the door to exploitation.

  • Post-exploitation steps:

    Once initial execution is achieved, we’ll show how attackers can perform lateral movement in the underlying infrastructure, such as:

    • Extracting sensitive secrets (cloud credentials, environment variables, connection strings).
    • Establishing persistence within the CI/CD pipeline (e.g., malicious jobs, trigger abuse, backdoor artifacts).

Part 2 – Defensive: How to Secure Your Pipelines in This New Model

With the offensive risks clearly laid out, we’ll move on to the defensive strategies. This section is divided into two phases:

  • Reinforcement and Protection:

    This proactive phase aims to secure the pipeline by design. We’ll cover:

    • Secure handling of secrets and credentials.
    • Hardening of CI/CD agents and build runners.
    • Implementation of integrity checks (e.g., checksum validation, signed commits, restricted runners).
    • Tightening access control and repository hygiene.
  • Detection and Monitoring:

    Even well-protected pipelines require active monitoring to catch suspicious activity. We’ll discuss:

    • CI/CD log analysis techniques.
    • Indicators of compromise in pipeline behavior.
    • Anomaly detection approaches tailored to build systems.
The speaker’s profile picture
Hugo

Passionate about programming, I began my career as a developer and private tutor in C/C++ before transitioning into offensive cybersecurity. For the past five years, I have worked as an offensive security auditor at Deloitte Cyber, where I conduct a wide range of penetration tests and technical audits. I am also responsible for designing and developing Pentest and Red Team infrastructure using Infrastructure as Code, with a strong focus on automation and operational efficiency.

This dual role - combining offensive security with infrastructure development - naturally led me to specialize in the security of CI/CD workflows. Through numerous audits and penetration tests for a wide range of clients across various environments, I have developed a deep and critical expertise in pipeline security, particularly within platforms such as Azure DevOps and GitHub Actions.