CVE-2026-53944

### Impact When making an external request, it is possible to bypass the IP filter that ensures the request isn't going to an internal service using an IPv6 literal which maps to a private IPv4 address. ### Vulnerable versions This vulnerability is present in Ghost from v6.0.9 up to v6.21.0. ### Patches v6.21.1 contains a fix for this issue. ### How to update For self-hosters using Docker, find [Docker's official Ghost image here](https://hub.docker.com/_/ghost). Updating a Docker-based Ghost instance [is documented here](https://docs.ghost.org/install/docker#updating-ghost). If your Ghost is a Ghost-CLI install see our documentation on [updating it to the latest version here](https://docs.ghost.org/update). ### References Ghost thanks [l3tchupkt](http://github.com/l3tchupkt) for disclosing this vulnerability responsibly. ### For more information If you have any questions or comments about this advisory, email us at [[email protected]](mailto:[email protected]).