CVE-2026-27707

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 0.5%, top 59% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.8Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation1% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
42%
KEV
Not listed

Published

February 27, 2026

Last Modified

June 17, 2026

Advisory Details (3)

Auto-updated Sep 14, 2026
Patch available. Sources: github_commit, github_release, github.
github Patch Available

Unauthenticated account registration on Plex-configured Seerr instances via Jellyfin authentication endpoint · Advisory · seerr-team/seerr · GitHub

https://github.com/seerr-team/seerr/security/advisories/GHSA-rc4w-7m3r-c2f7
github_release Patch Available

Release v3.1.0

Patch available: seerr-team/seerr v3.1.0

https://github.com/seerr-team/seerr/releases/tag/v3.1.0
github_commit Patch Available

commit 4ae20684092b (seerr-team/seerr)

Patch available: seerr-team/seerr v3.1.0 (contains commit 4ae20684092b)

https://github.com/seerr-team/seerr/commit/4ae20684092b5b28527b23dfbc1a3417858fee8e

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 5× in last 7d / 27× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-13 16:47 UTCEPSS rescore
  2. 2026-09-12 15:01 UTCEPSS rescore
  3. 2026-09-11 14:52 UTCEPSS rescore
  4. 2026-09-10 09:34 UTCEPSS rescore
  5. 2026-09-08 22:00 UTCEPSS rescore
  6. 2026-09-07 16:01 UTCEPSS rescore
  7. 2026-09-06 13:47 UTCEPSS rescore
  8. 2026-09-06 13:47 UTCEPSS rescore
  9. 2026-09-04 05:06 UTCEPSS rescore
  10. 2026-09-02 14:11 UTCEPSS rescore
  11. 2026-09-01 13:53 UTCEPSS rescore
  12. 2026-09-01 04:39 UTCEPSS rescore
  13. 2026-09-01 04:39 UTCEPSS rescore
  14. 2026-09-01 01:04 UTCOSV refresh
  15. 2026-08-30 19:17 UTCEPSS rescore
  16. 2026-08-30 01:22 UTCEPSS rescore
  17. 2026-08-28 21:41 UTCEPSS rescore
  18. 2026-08-27 14:25 UTCEPSS rescore
  19. 2026-08-26 14:46 UTCEPSS rescore
  20. 2026-08-25 13:48 UTCEPSS rescore
  21. 2026-08-23 00:19 UTCEPSS rescore
  22. 2026-08-21 23:49 UTCEPSS rescore
  23. 2026-08-20 22:55 UTCEPSS rescore
  24. 2026-08-19 17:03 UTCEPSS rescore
  25. 2026-08-18 13:48 UTCEPSS rescore
Show 31 more
  1. 2026-08-17 13:47 UTCEPSS rescore
  2. 2026-08-16 14:56 UTCEPSS rescore
  3. 2026-08-16 02:14 UTCEPSS rescore
  4. 2026-08-15 01:30 UTCEPSS rescore
  5. 2026-08-14 08:49 UTCEG score recompute
  6. 2026-08-13 22:00 UTCEPSS rescore
  7. 2026-08-13 00:45 UTCEG score recompute
  8. 2026-08-12 13:50 UTCEPSS rescore
  9. 2026-08-11 23:33 UTCEG score recompute
  10. 2026-08-11 13:42 UTCEPSS rescore
  11. 2026-08-11 06:08 UTCEG score recompute
  12. 2026-08-11 00:00 UTCEPSS rescore
  13. 2026-08-09 17:44 UTCEG score recompute
  14. 2026-08-09 13:46 UTCEPSS rescore
  15. 2026-08-09 08:27 UTCEG score recompute
  16. 2026-08-08 16:37 UTCEPSS rescore
  17. 2026-08-07 20:26 UTCEG score recompute
  18. 2026-08-06 13:46 UTCEPSS rescore
  19. 2026-08-06 02:53 UTCEG score recompute
  20. 2026-08-05 19:17 UTCEPSS rescore
  21. 2026-08-04 15:10 UTCEPSS rescore
  22. 2026-08-04 04:52 UTCEG score recompute
  23. 2026-08-03 10:36 UTCEPSS rescore
  24. 2026-08-02 19:20 UTCEG score recompute
  25. 2026-08-02 02:26 UTCEPSS rescore
  26. 2026-08-01 04:16 UTCEPSS rescore
  27. 2026-07-30 16:27 UTCEPSS rescore
  28. 2026-07-30 01:30 UTCEPSS rescore
  29. 2026-07-28 15:36 UTCEPSS rescore
  30. 2026-07-27 14:03 UTCEG score recompute
  31. 2026-07-27 13:55 UTCOSV refresh

Frequently asked(5)

What is CVE-2026-27707?
CVE-2026-27707 is a critical vulnerability published on February 27, 2026. 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…
When was CVE-2026-27707 disclosed?
CVE-2026-27707 was first published in the National Vulnerability Database on February 27, 2026, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-27707 actively exploited?
CVE-2026-27707 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 58.3% of all scored CVEs.
What is the CVSS score of CVE-2026-27707?
CVE-2026-27707 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-27707?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-27707, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-27707

Explore →

Is Your Infrastructure Affected by CVE-2026-27707?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs