Exploiting AWS CodeBuild Memory Dumps: How Attackers Stole Repo Tokens

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Introduction:

A recent security breach involving the Q Developer extension backdoor revealed that attackers gained write access to a repository by stealing a token via AWS CodeBuild memory dumps. This technique highlights critical vulnerabilities in cloud CI/CD pipelines and underscores the need for hardened security practices.

Learning Objectives:

  • Understand how AWS CodeBuild memory dumps can expose sensitive credentials.
  • Learn mitigation techniques to secure CI/CD pipelines from token theft.
  • Implement best practices for monitoring and restricting AWS IAM permissions.

1. How AWS CodeBuild Memory Dumps Leak Tokens

Verified Exploit Scenario:

Attackers extracted AWS credentials from memory dumps in CodeBuild environments, allowing them to escalate privileges and push malicious code.

Step-by-Step Exploitation:

  1. Trigger a CodeBuild Project with a malicious build script: 
    Malicious buildspec.yml to dump memory 
phases: 
build: 
commands: </li>
</ol>

- cat /proc/self/environ | grep AWS 
- strings /proc/self/maps | grep AWS_SECRET

    2. Exfiltrate exposed AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY from logs.

    1. Use stolen credentials to push code or escalate access.

    Mitigation:

    • Restrict CodeBuild IAM roles with least privilege.
    • Enable CloudTrail logging to monitor unusual API calls.

    2. Detecting Stolen Tokens in AWS

    Verified AWS CLI Command to Check Active Keys:

    aws iam list-access-keys --user-name <USER>

    Steps to Investigate:

    1. Review CloudTrail logs for unexpected `sts:AssumeRole` or `codebuild:StartBuild` events.

    2. Rotate exposed keys immediately:

    aws iam update-access-key --access-key-id <KEY_ID> --status Inactive

    3. Securing CodeBuild with IAM Policies

    Restrictive IAM Policy Example:

    {
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Deny",
"Action": [
"iam:CreateAccessKey",
"sts:AssumeRole"
],
"Resource": ""
}
]
}

    Implementation Steps:

    1. Attach policy to CodeBuild service roles.

    2. Use AWS Organizations SCPs to enforce restrictions.

    4. Preventing Memory Dumps in CI/CD Pipelines

    Linux Hardening Command:

     Disable core dumps in /etc/security/limits.conf 
 hard core 0

    Mitigation Steps:

    1. Disable core dumps in build environments.

    2. Use ephemeral containers with no persistent storage.

    5. Monitoring for Suspicious Activity

    AWS GuardDuty Setup:

    aws guardduty create-detector --enable

    Key Alerts to Enable:

    – `UnauthorizedAccess:IAMUser/InstanceCredentialExfiltration`
    – `PenTest:IAMUser/CodeBuildPermissions`

    What Undercode Say:

    • Key Takeaway 1: Attackers increasingly target CI/CD pipelines via memory leaks—hardening build environments is critical.
    • Key Takeaway 2: AWS IAM policies must follow zero-trust principles to prevent lateral movement.

    Analysis:

    This breach demonstrates how cloud-native attacks evolve beyond traditional endpoints. Organizations must audit CodeBuild permissions, enforce memory protections, and monitor unusual credential usage. Future attacks may leverage similar techniques against GitHub Actions and Azure Pipelines, making proactive security essential.

    Prediction:

    As CI/CD adoption grows, attackers will develop more sophisticated memory-scraping malware, necessitating hardened runtime controls and behavioral detection in cloud environments. Companies ignoring these risks face supply chain compromises and repo hijacking.

    IT/Security Reporter URL:

    Reported By: Nick Frichette – Hackers Feeds
    Extra Hub: Undercode MoN
    Basic Verification: Pass ✅

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