Vulnerability in Jellyfin (CVE-2026-35031)
Summary
Vulnerability in Jellyfin (CVE-2026-35031). Successful exploitation can lead to full system takeover. Exploitable via POST /Videos/{itemId}/Subtitles.
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 vulnerability chain in the subtitle upload endpoint (POST /Videos/{itemId}/Subtitles), where the Format field is not validated, allowing path traversal via the file extension and enabling arbitrary file write. This arbitrary file write can be chained into arbitrary file read via .strm files, database extraction, admin privilege escalation, and ultimately remote code execution as root via ld.so.preload. Exploitation requires an administrator account or a user that has been explicitly granted the "Upload Subtitles" permission. This issue has been fixed in version 10.11.7. If users are unable to upgrade immediately, they can grant non-administrator users Subtitle upload permissions to reduce attack surface.
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-2026-35031 has been found in Jellyfin.
Attackers can target a specific entry point like POST /Videos/{itemId}/Subtitles over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 9.9/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Jellyfin CVE-2026-35031" on the vendor's site.
CVE-2026-35031 (Jellyfin) — CWE-20 / CVSS v3 9.9
Attack vector: remote (network-reachable) / no user interaction
Attack surface: POST /Videos/{itemId}/Subtitles
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-20) exists in Jellyfin. Attackers reach the vulnerable code path via POST /Videos/{itemId}/Subtitles.
Check the vendor advisory for the affected versions of Jellyfin. Attack surface: POST /Videos/{itemId}/Subtitles.
Severity: Critical (CVSS 9.9/10). Successful exploitation can lead to full system takeover.
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 /Videos/{itemId}/Subtitles 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 /Videos/{itemId}/Subtitles' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
POST /Videos/{itemId}/Subtitles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 /Videos/{itemId}/Subtitles 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