{"id":"CVE-2026-27707","summary":"Plex-configured Seerr instances vulnerable to unauthenticated account registration via Jellyfin authentication endpoint","details":"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.","aliases":["GHSA-rc4w-7m3r-c2f7"],"modified":"2026-04-02T13:22:22.147948Z","published":"2026-02-27T19:29:18.768Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27707.json","cwe_ids":["CWE-288","CWE-807"],"cna_assigner":"GitHub_M"},"references":[{"type":"WEB","url":"https://github.com/seerr-team/seerr/releases/tag/v3.1.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27707.json"},{"type":"ADVISORY","url":"https://github.com/seerr-team/seerr/security/advisories/GHSA-rc4w-7m3r-c2f7"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27707"},{"type":"FIX","url":"https://github.com/seerr-team/seerr/commit/4ae20684092b5b28527b23dfbc1a3417858fee8e"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/seerr-team/seerr","events":[{"introduced":"63dfe003b0852d6307772abd331ffde8686e8c17"},{"fixed":"94a70bb5fc9a4486857071a6fc048c8081fa7ca9"}]}],"versions":["v2.0.0","v2.0.1","v2.1.0","v2.2.0","v2.2.1","v2.2.2","v2.2.3","v2.3.0","v2.4.0","v2.5.0","v2.5.1","v2.5.2","v2.6.0","v2.7.0","v2.7.1","v2.7.2","v2.7.3","v3.0.0","v3.0.1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-27707.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L"}]}