You have stored company approved compute images in a single Google Cloud project that is...

To grant read access to a third-party disk image stored in an external Google Cloud organization so it can be deployed into a VPC Service Controls perimeter, you need to update the service perimeter to allow egress traffic from your projects to the external project.

Update the Service Perimeter:

Go to the Google Cloud Console, navigate to Security > VPC Service Controls.

Select the appropriate service perimeter that includes your image repository project.

Configure Egress Policy:

Within the perimeter settings, configure the egressTo field to allow traffic to the external project.

Set the identityType to ANY_IDENTITY to permit any principal to access the external project for this specific egress rule.

Specify External Project and Service:

In the egressFrom field, include the external Google Cloud project number as an allowed resource.

Set the serviceName to compute.googleapis.com to specifically allow access to the Compute Engine service in the external project.

This configuration permits your internal projects to read the disk image from the external project while maintaining the security boundaries established by the service perimeter.

VPC Service Controls Documentation

Configuring Service Perimeters