CVE-2026-43986: Tautulli vulnerable to unauthenticated SSRF in /image/<hash> via attacker-seeded image hash replay

Synopsis

This is a server-side request forgery (SSRF) vulnerability in Tautulli, a Python-based monitoring tool for Plex Media Server. A low-privilege authenticated user can seed a malicious URL into Tautulli's internal image hash lookup table, and from that point on any unauthenticated external user can trigger the Tautulli or Plex Media Server host to fetch arbitrary attacker-chosen URLs by requesting a public `/image/<hash>` endpoint. Successful exploitation enables internal network scanning, exfiltration of cloud metadata credentials, and further lateral movement against services reachable from the Tautulli host. A patched-image rebuild at version 2.17.1 is available on HarborGuard for environments running an affected version.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must reach the Tautulli service over the network to seed the malicious hash entry and to trigger the unauthenticated `/image/<hash>` endpoint.

• AuthenticationRequired

  Seeding the malicious image hash requires a low-privilege authenticated account (such as a guest user), though any account type is sufficient; subsequent exploitation of the seeded hash is fully unauthenticated.

• Victim interactionNot required

  No victim interaction is needed; once the malicious hash entry is seeded, the SSRF can be triggered by any external HTTP request without user involvement.

• Attack complexityDetail

  Attack complexity is low, meaning the exploit is reliable and requires no special timing, race conditions, or environmental prerequisites beyond having a valid low-privilege account for the initial seeding step.

Blast Radius

• The Tautulli or Plex Media Server host fetches arbitrary attacker-chosen URLs, enabling full internal network scanning against services not otherwise exposed externally.
• Cloud instance metadata endpoints (such as the AWS EC2 metadata service at 169.254.169.254) are reachable, allowing an attacker to read IAM role credentials and session tokens.
• Internal administrative APIs and unauthenticated management interfaces on the host network can be probed and interacted with via the forged server-side requests.
• The vulnerability is persistent once seeded: the malicious hash entry remains in the lookup table and can be repeatedly triggered by any external user until the entry is purged or the service is patched.