CVE-2023-23939 : Exploit Details and Defense Strategies

This CVE-2023-23939 focuses on an escalation of privilege vulnerability found in Azure/setup-kubectl for versions prior to version 3, impacting GitHub users utilizing this GitHub Action.

Understanding CVE-2023-23939

Azure/setup-kubectl is a GitHub Action used for installing Kubectl, a command-line tool for interacting with Kubernetes clusters. The vulnerability allows unauthorized actors on the Actions runner to replace the Kubectl binary due to insecure file creation and permission assignment, leading to potential privilege escalation.

What is CVE-2023-23939?

The vulnerability in Azure/setup-kubectl arises from the insecure temporary creation of a file that allows any local user to replace the Kubectl binary, typically leading to privilege escalation, especially for users with root access. The issue occurs due to incorrect permission assignment for critical resources, making it exploitable if an attacker breaches the GitHub actions runner or maliciously executes an attack through an affected Action.

The Impact of CVE-2023-23939

The impact of this vulnerability is categorized as low severity with a base CVSS score of 3.9. Although the availability impact is low, the potential for privilege escalation poses a security risk to affected users. This issue has been addressed in versions

v3

and later, using more secure permissions to mitigate the risk.

Technical Details of CVE-2023-23939

Azure/setup-kubectl vulnerability is classified under CWE-732: Incorrect Permission Assignment for Critical Resource.

Vulnerability Description

The vulnerability allows unauthorized users to replace the Kubectl binary due to world-writable file creation and insecure permission settings, leading to potential privilege escalation.

Affected Systems and Versions

Vendor: Azure
Product: setup-kubectl
Affected Versions: < 3

Exploitation Mechanism

Unauthorized actors on the Actions runner can exploit the vulnerability by replacing the Kubectl binary through insecure file creation and incorrect permission assignment, potentially escalating their privileges.

Mitigation and Prevention

It is crucial for users to take immediate steps to address and prevent the CVE-2023-23939 vulnerability to ensure the security of their environments.

Immediate Steps to Take

Upgrade to version 3 or later of Azure/setup-kubectl to mitigate the vulnerability.
Follow best practices for securing GitHub Actions runners and review permissions assigned to critical resources.

Long-Term Security Practices

Regularly monitor and update GitHub Actions dependencies to ensure the latest security patches are applied.
Conduct security assessments and audits of GitHub Actions used in the workflow to identify and address potential vulnerabilities proactively.

Patching and Updates

Ensure that all GitHub Actions used in the workflow are updated to the latest secure versions to prevent exploitation of known vulnerabilities.
Stay informed about security advisories and updates from GitHub and related providers to keep the environment secure.