The flaw is in the /pms_image_proxy endpoint of Tautulli, which is left unprotected by authentication. A user can supply any http:// or https:// URL in the img parameter; the backend forwards this to the Plex Media Server’s photo transcode service without checking the target address. This turns the Plex process into a proxy that can contact any address reachable from the host, such as internal servers, the Internet, or even RFC‑1918 destinations. The attacker can therefore exfiltrate data, discover services, or perform internal reconnaissance without needing credentials. The weakness is a server‑side request forgery (CWE‑918).

Tautulli, the monitoring component for Plex Media Server, is affected. Any installation running a version earlier than 2.17.0 is vulnerable. The bug was fixed in release 2.17.0, so upgrades to that or later versions remove the issue.

The CVSS base score of 4.0 indicates moderate risk. The EPSS score is below 1%, suggesting that exploitation is currently unlikely, and the weakness is not listed in the CISA KEV catalog. However, the method requires only unauthenticated HTTP access to the Tautulli web interface, making the attack surface wide. A threat actor could exploit the flaw by sending a crafted request to the unprotected endpoint and directing the Plex Media Server to reach internal or external URLs. The lack of authentication and hostname restriction makes exploitation straightforward if the web service is publicly reachable.