# CVE-2026-27707: Plex-configured Seerr instances vulnerable to unauthenticated account registration via Jellyfin authentication endpoint

> Unauthenticated attackers can register accounts on Plex-configured Seerr instances via a flawed Jellyfin endpoint, gaining access to submit media requests.

- **Severity:** High 7.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 Feb 2026
- **Updated:** 27 Feb 2026
- **Also known as:** GHSA-rc4w-7m3r-c2f7

## What is CVE-2026-27707?

CVE-2026-27707 is a high-severity authentication bypass vulnerability in seerr-team seerr, published on 27 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-807 (Reliance on Untrusted Inputs in a Security Decision), CWE-288 (Authentication Bypass Using an Alternate Path or Channel)

## Which versions are affected by CVE-2026-27707?

It affects 1 product.


Products: Seerr Seerr.

## How do I fix CVE-2026-27707?

No fix has been published for CVE-2026-27707 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-27707 being exploited?

There is no known exploitation of CVE-2026-27707 in the wild and no public exploit code.

## Other vulnerabilities in seerr-team seerr

- [CVE-2026-27793](https://insights.sbomify.com/CVE-2026-27793/): Seerr has Broken Object-Level Authorization in User Profile Endpoint that Exposes Third-Party Notification Credentials (medium 6.5)
- [CVE-2026-27792](https://insights.sbomify.com/CVE-2026-27792/): Seerr missing authentication on pushSubscription endpoints (medium 5.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27707 and fix it if it is affected.

What it is: CVE-2026-27707 is a high-severity authentication bypass vulnerability in seerr-team seerr, published on 27 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-27707 in the wild and no public exploit code.

Affected product: seerr-team seerr. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-27707/ (Markdown: https://insights.sbomify.com/CVE-2026-27707/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27707
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27707
- OSV: https://osv.dev/vulnerability/CVE-2026-27707

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27707/
Summaries are generated and may contain mistakes; the official description above is the record.