{"id":"CVE-2026-27707","state":"PUBLISHED","title":"Plex-configured Seerr instances vulnerable to unauthenticated account registration via Jellyfin authentication endpoint","description":"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.","publishedAt":"2026-02-27T19:29:18.768Z","updatedAt":"2026-02-27T20:22:24.091Z","severity":{"score":7.3,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L","source":"GitHub_M"},"assigner":"GitHub_M","products":["seerr-team seerr"],"affected":[{"vendor":"seerr-team","product":"seerr","versions":[{"version":">= 2.0.0, < 3.1.0","status":"affected"}]}],"references":["https://github.com/seerr-team/seerr/security/advisories/GHSA-rc4w-7m3r-c2f7","https://github.com/seerr-team/seerr/commit/4ae20684092b5b28527b23dfbc1a3417858fee8e","https://github.com/seerr-team/seerr/releases/tag/v3.1.0"],"weaknesses":["CWE-288","CWE-807"],"ingestedAt":"2026-10-29T20:11:31.369Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/27xxx/CVE-2026-27707.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-27707","state":"PUBLISHED","datePublished":"2026-02-27T19:29:18.768Z","dateUpdated":"2026-02-27T20:22:24.091Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-02-23T17:56:51.203Z"},"containers":{"cna":{"title":"Plex-configured Seerr instances vulnerable to unauthenticated account registration via Jellyfin authentication endpoint","descriptions":[{"lang":"en","value":"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":[{"vendor":"seerr-team","product":"seerr","versions":[{"version":">= 2.0.0, < 3.1.0","status":"affected"}]}],"references":[{"url":"https://github.com/seerr-team/seerr/security/advisories/GHSA-rc4w-7m3r-c2f7","name":"https://github.com/seerr-team/seerr/security/advisories/GHSA-rc4w-7m3r-c2f7","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/seerr-team/seerr/commit/4ae20684092b5b28527b23dfbc1a3417858fee8e","name":"https://github.com/seerr-team/seerr/commit/4ae20684092b5b28527b23dfbc1a3417858fee8e","tags":["x_refsource_MISC"]},{"url":"https://github.com/seerr-team/seerr/releases/tag/v3.1.0","name":"https://github.com/seerr-team/seerr/releases/tag/v3.1.0","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"LOW","baseScore":7.3,"baseSeverity":"HIGH","confidentialityImpact":"LOW","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-288","lang":"en","description":"CWE-288: Authentication Bypass Using an Alternate Path or Channel","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-807","lang":"en","description":"CWE-807: Reliance on Untrusted Inputs in a Security Decision","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-02-27T19:32:07.180Z"},"source":{"advisory":"GHSA-rc4w-7m3r-c2f7","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-02-27T20:22:11.831766Z","id":"CVE-2026-27707","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-02-27T20:22:24.091Z"}}]}}}