CVE-2025-7342 – Root Access Risk in Kubernetes Image Builder

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Summary

CVE-2025-7342 is a high-severity vulnerability in the Kubernetes Image Builder project—specifically affecting builds that utilize either the Nutanix or OVA (Open Virtual Appliance) providers. The flaw allows attackers to inject content with root privileges during image creation, resulting in images that can be silently compromised prior to deployment.

This vulnerability could allow a malicious actor with access to the build process or environment to introduce backdoors, alter system binaries, or install persistent malware that runs at the root level once the image is deployed in production environments.

Affected Components

Vulnerable:

• Tool: Kubernetes Image Builder
• Versions: v0.1.44 and earlier
• Providers:
• Nutanix
• OVA (Open Virtual Appliance)

Not Affected:

• Builds using other provider types (e.g., AWS, Azure, vSphere, etc.)
• Kubernetes Image Builder v0.1.45 and later
• Builds run in properly sandboxed or hardened environments

Technical Details

What is Kubernetes Image Builder?

Kubernetes Image Builder is a tool used to automate the creation of machine images (e.g., for KubeVirt, Nutanix, VMware, or cloud platforms) preloaded with required Kubernetes components, OS configurations, and customizations.

It supports multiple builders or providers, such as:

• AMI (Amazon)
• VHD (Azure, Hyper-V)
• OVA (VMware, Nutanix)
• RAW/ISO builds

What Went Wrong?

In builds using Nutanix or OVA providers, the image-building process did not correctly lock down file ownership or privilege elevation in temporary directories or provisioning hooks. This leads to the following issues:

• Attackers (or misconfigured scripts) could place or alter files in the build context that end up with root-level permissions in the final image
• Default hardening steps were skipped or misconfigured, particularly around system binaries or user profiles
• The images produced may contain unexpected services, scheduled tasks, SSH keys, or binaries injected with root ownership

Exploitable Scenario:

1. An attacker has access to the build environment (even limited).
2. During image creation using Nutanix or OVA providers, the attacker places malicious content in expected provisioning directories or post-process steps.
3. The final image is deployed automatically to production Kubernetes nodes or systems, unaware of compromise.
4. The attacker can leverage a backdoor, SSH key, or systemd service for persistent root access.

Exploitation Impact

Risk Type Details Privilege Escalation Injected content runs as root in the image Persistence Backdoors or cron jobs may silently remain post-deployment Confidentiality Data leakage or unauthorized data access due to rogue binaries Integrity Trust in golden/base images compromised Availability Deployed nodes may be remotely controlled or taken offline

Impact extends to all systems built using affected images or deployments that trust compromised image artifacts.

Mitigation & Recommendations

Immediate Actions:

• Upgrade to Kubernetes Image Builder v0.1.45 or later
  ➤ This version includes fix patches for the insecure privilege escalation vulnerability
• Audit existing image artifacts built using:
• Nutanix provider
• OVA provider
• Any automated or CI/CD pipeline with unreviewed access
• Check for signs of compromise in deployed systems, like:
• Unexpected user accounts
• Unknown systemd services
• Modified /etc/rc.local, /etc/passwd, or cron entries
• Unrecognized SSH keys in /root/.ssh/authorized_keys
• Verify hashes, checksums, and package manifests of your golden images to detect tampering

Long-term Hardening:

• Avoid running image builds with host-level root access unless isolated in containers or VMs
• Implement read-only build environments and image hash verification in your CI/CD and deployment pipelines
• Limit use of community-built or shared provisioning scripts unless audited
• Introduce image signing practices (via tools like Cosign or Notary)

Exposure Context

Kubernetes Image Builder is often used in:

• Cluster API (CAPI) pipelines
• Infrastructure as Code (IaC) tools (e.g., Terraform, Ansible)
• Custom OS base image pipelines for Kubernetes Cluster nodes

Misconfigured or compromised machine images can indirectly affect production clusters across AWS, GCP, Azure, vSphere, Nutanix, or on-prem bare metal.