CVE-2026-27707

CRITICALNVD 9.89.8
EchelonGraph scoreLOW confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). 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: 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(low)
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%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
40%
KEV
Not listed

Published

February 27, 2026

Last Modified

June 17, 2026

Advisory Details (3)

Auto-updated Jul 27, 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 2× in last 7d / 2× 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. 2026-07-27 14:03 UTCEG score recompute
  2. 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 59.7% 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). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
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

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