CVE-2024-9486: Kubernetes Image Builder Privilege Escalation

CVE-2024-9486 Overview

A critical security vulnerability has been discovered in the Kubernetes Image Builder affecting versions <= v0.1.37. The vulnerability stems from default credentials that are enabled during the image build process and are not properly disabled in virtual machine images built using the Proxmox provider. This creates a severe security risk where nodes using the resulting images become accessible via these default credentials, potentially allowing attackers to gain root access to affected Kubernetes cluster nodes.

Critical Impact

Attackers can leverage default credentials to gain root access to Kubernetes cluster nodes built with the affected Image Builder Proxmox provider, potentially compromising entire cluster infrastructure.

Affected Products

• Kubernetes-sigs Image Builder versions <= v0.1.37
• Virtual machine images built using the Proxmox provider
• Kubernetes clusters using VM images created via Image Builder with Proxmox provider

Discovery Timeline

• 2024-10-15 - CVE-2024-9486 published to NVD
• 2025-12-08 - Last updated in NVD database

Technical Details for CVE-2024-9486

Vulnerability Analysis

This vulnerability is classified as CWE-798 (Use of Hard-coded Credentials), representing a fundamental insecure default configuration issue in the Kubernetes Image Builder's Proxmox provider workflow. During the image build process, default credentials are enabled to facilitate provisioning and configuration. However, the critical security flaw occurs because these credentials are not disabled or removed before the image is finalized.

The vulnerability affects the entire trust chain of VM image deployment in Kubernetes environments. When organizations build VM images using the Proxmox provider and deploy them as Kubernetes nodes, every deployed node inherits these default credentials, creating a consistent attack surface across the infrastructure.

Root Cause

The root cause is an insecure default configuration in the Image Builder's Proxmox provider implementation. The build process requires temporary credentials for image provisioning, but the workflow fails to include a cleanup step to disable or remove these credentials from the final image. This is a classic example of hardcoded credentials (CWE-798) where security-sensitive authentication material persists beyond its intended temporary use.

Attack Vector

The attack vector is network-based, requiring no authentication, no user interaction, and low complexity to exploit. An attacker with network access to vulnerable Kubernetes nodes can:

1. Identify nodes built using affected Image Builder versions with the Proxmox provider
2. Connect to these nodes using the well-known default credentials
3. Authenticate successfully and obtain root-level access
4. Pivot within the Kubernetes cluster or exfiltrate sensitive data

The default credentials are publicly known, making exploitation trivial once vulnerable nodes are identified. Attackers can scan for exposed SSH services and attempt authentication with these default credentials to identify vulnerable systems.

Detection Methods for CVE-2024-9486

Indicators of Compromise

• Unexpected SSH authentication events using default or builder accounts on Kubernetes nodes
• Unauthorized root-level access attempts from external IP addresses
• Authentication logs showing successful logins with credentials that should not exist in production
• Unusual process execution or privilege escalation on nodes built with affected Image Builder versions

Detection Strategies

• Audit all Kubernetes node images to verify they were not built using Image Builder versions <= v0.1.37 with the Proxmox provider
• Implement SSH authentication monitoring to detect login attempts using default credentials
• Review system user accounts on VM images for unexpected default users with elevated privileges
• Deploy network intrusion detection rules to identify credential-based attacks targeting known default accounts

Monitoring Recommendations

• Enable comprehensive logging for SSH authentication events across all Kubernetes nodes
• Monitor for lateral movement patterns from compromised nodes within the cluster
• Implement alerts for any successful authentication to production nodes using non-standard accounts
• Conduct periodic image audits to ensure compliance with secure build practices

How to Mitigate CVE-2024-9486

Immediate Actions Required

• Upgrade Kubernetes Image Builder to a patched version that addresses CVE-2024-9486
• Rebuild all VM images that were created using the Proxmox provider with affected versions
• Manually disable or remove default credentials from existing deployed nodes as an interim measure
• Rotate all credentials and secrets on potentially compromised nodes
• Conduct a security review of all Kubernetes nodes for signs of unauthorized access

Patch Information

The Kubernetes SIG has addressed this vulnerability through Pull Request #1595. Organizations should upgrade to the patched version of Image Builder and rebuild all VM images using the Proxmox provider. Additional details are available in the Kubernetes Security Announcement and the GitHub Issue Discussion.

Workarounds

• Manually disable default credentials on all deployed nodes built with affected versions before the rebuild
• Implement network segmentation to restrict SSH access to Kubernetes nodes from trusted sources only
• Deploy additional authentication controls such as SSH key-based authentication and disable password authentication entirely
• Use configuration management tools to audit and remediate default credentials across the node fleet

# Example: Disable password authentication and restrict SSH access
# Add to /etc/ssh/sshd_config on affected nodes
PasswordAuthentication no
PermitRootLogin no
AllowUsers authorized_admin_user