CVE-2026-27707Public exploitNetwork attack vector

Unauthenticated account registration via faulty Jellyfin guard

Published Feb 27, 2026 · Updated Feb 27, 2026

Authentication bypass in Seerr 2.0.0 through 3.0.1 allows remote attackers to register accounts through the Jellyfin login endpoint. In server/routes/auth.ts, the guard incorrectly treats an empty stored Jellyfin address as permission to continue and accepts attacker-supplied server details. Exposure requires a Plex-configured instance with Jellyfin never configured and new Plex login enabled; successful abuse grants a default session able to submit media requests.

CVSS severity7.3
High
EPSS probability0.51%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Seerr 2.0.0 through 3.0.1 allows remote attackers to register accounts through the Jellyfin login endpoint. In server/routes/auth.ts, the guard incorrectly treats an empty stored Jellyfin address as permission to continue and accepts attacker-supplied server details. Exposure requires a Plex-configured instance with Jellyfin never configured and new Plex login enabled; successful abuse grants a default session able to submit media requests.

The record

CVE
CVE-2026-27707
Published
Feb 27, 2026
Updated
Feb 27, 2026
Vendor
Seerr Team
Product
Seerr
Classifications
CWE-807, CWE-288, T1136
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 2.0.0, < 3.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Seerr Team · Seerrversion=>= 2.0.0, < 3.1.0

Published CVSS scores

7.3GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-807Reliance on Untrusted Inputs in a Security Decision
CWE-288Authentication Bypass Using an Alternate Path or Channel
T1136Create Account

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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