Ghost: Server-side request forgery via DNS rebinding in external request handling

Ghost is a Node.js content management system. From 6.0.9 until 6.21.1, Ghost’s private-IP check for outbound HTTP requests could be bypassed via DNS rebinding, allowing an attacker to coerce the Ghost server into reaching hosts on internal networks through features that issue external fetches. This vulnerability is fixed in 6.21.1.