CVE-2026-35034
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedJellyfin is an open source self hosted media server. Versions prior to 10.11.7 contain a denial of service vulnerability in the SyncPlay group creation endpoint (POST /SyncPlay/New), where an authenticated user can create groups with names of unlimited size due to insufficient input validation. By sending large payloads combined with arbitrary group IDs, an attacker can lock out the endpoint for other clients attempting to join SyncPlay groups and significantly increase the memory usage of the Jellyfin process, potentially leading to an out-of-memory crash. This issue has been fixed in version 10.11.7.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceJellyfin versions prior to 10.11.7 have a denial of service vulnerability in the SyncPlay group creation endpoint (POST /SyncPlay/New). The endpoint lacks input validation on the group name parameter, allowing authenticated users to submit groups with unlimited-length names. Attackers can send large payloads with arbitrary group IDs to exhaust server memory and lock out legitimate users from joining SyncPlay groups, potentially causing an out-of-memory crash.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 10.11.7CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify installed Jellyfin versionCheck your Jellyfin server version through the web UI (Dashboard > General > Version) or by inspecting the jellyfin-web.jar or docker container tag, or running 'jellyfin --version' if using the binaryAffected if Version is below 10.11.7 (e.g., 10.11.6, 10.10.x, 10.9.x, etc.)
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Verify SyncPlay plugin is enabledNavigate to Dashboard > Plugins > SyncPlay in the Jellyfin web interface, or inspect the plugins configuration file in the Jellyfin data directoryAffected if SyncPlay plugin is installed and enabled on the server
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Confirm authenticated access to SyncPlay endpointReview user permissions in Dashboard > Users to determine if regular authenticated users can access SyncPlay functionality; check if anonymous access is permitted in SyncPlay settingsAffected if Authenticated (non-admin) users have access to create SyncPlay groups
Your environment is affected if you are running Jellyfin versions prior to 10.11.7 with the SyncPlay feature enabled and accessible to authenticated users, as this allows the DoS condition on the /SyncPlay/New endpoint.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped10.11.7
Upgrade Jellyfin to version 10.11.7 or later. Additionally, implement input validation enforcing reasonable length limits on SyncPlay group names to prevent similar issues.
Jellyfin 10.11.7 or later
- Backup your Jellyfin configuration and data directory before proceeding
- Stop the Jellyfin service
- Upgrade Jellyfin to version 10.11.7 or later using your package manager or by downloading the latest release from the official Jellyfin website
- Verify the installed version matches the fixed release (10.11.7 or higher)
- Restart the Jellyfin service
- Test the SyncPlay functionality to confirm the endpoint now properly validates group names and accepts bounded input sizes
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2026-35034 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-35034 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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