Vulnerability in Jellyfin (CVE-2026-35034)
Summary
Vulnerability in Jellyfin (CVE-2026-35034). Risk of unauthorized operations or information disclosure. Exploitable via POST /SyncPlay/New.
Original description
The description as published by the source.
Jellyfin 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.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-35034 has been found in Jellyfin.
Attackers can target a specific entry point like POST /SyncPlay/New over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 6.5/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Jellyfin CVE-2026-35034" on the vendor's site.
CVE-2026-35034 (Jellyfin) — CWE-400 / CVSS v3 6.5
Attack vector: remote (network-reachable) / no user interaction
Attack surface: POST /SyncPlay/New
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-400) exists in Jellyfin. Attackers reach the vulnerable code path via POST /SyncPlay/New.
Check the vendor advisory for the affected versions of Jellyfin. Attack surface: POST /SyncPlay/New.
Severity: Medium (CVSS 6.5/10). Risk of unauthorized operations or information disclosure.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual POST /SyncPlay/New requests with malformed payloads or SQL meta-characters. Run grep -r 'Jellyfin' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'Jellyfin' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
Jellyfinを grep し、稼働しているサービス・バージョンを把握する。 -
2Hunt for indicators of compromise detect
grep 'POST /SyncPlay/New' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
POST /SyncPlay/Newへの異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。 -
3Post-deployment verification verify
Replay attack against POST /SyncPlay/New on staging to confirm patch closes the vectorパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 2 と同じログクエリでアラート再発が無いか継続監視。
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- web github.com