CVE-2026-27707

Summary

Seerr is an open-source media request and discovery manager for Jellyfin, Plex, and Emby. Starting in version 2.0.0 and prior to version 3.1.0, an authentication guard logic flaw in POST /api/v1/auth/jellyfin allows an unauthenticated attacker to register a new Seerr account on any Plex-configured instance by authenticating with an attacker-controlled Jellyfin server. The attacker receives an authenticated session and can immediately use the application with default permissions, including the ability to submit media requests to Radarr/Sonarr. Any Seerr deployment where all three of the following are true may be vulnerable: settings.main.mediaServerType is set to PLEX (the most common deployment).; settings.jellyfin.ip is set to "" (default, meaning Jellyfin was never configured); and settings.main.newPlexLogin is set to true (default). Jellyfin-configured and Emby-configured deployments are not affected. Version 3.1.0 of Seerr fixes this issue.

Affected Software

VendorProductVersion RangeStatus
seerr-teamseerr>= 2.0.0, < 3.1.0affected

Weaknesses

  • CWE-288: CWE-288: Authentication Bypass Using an Alternate Path or Channel
  • CWE-807: CWE-807: Reliance on Untrusted Inputs in a Security Decision

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: yes
    • Technical Impact: partial

References