Path Traversal in Jellyfin (CVE-2026-49247)
Summary
Path traversal in Jellyfin (CVE-2026-49247). Successful exploitation can lead to full system takeover. Exploitable via POST /ClientLog/Document. Mitigation: upgrade to 10.11.10 or later.
Original description
The description as published by the source.
Jellyfin is an open source self hosted media server. From 10.9.0 until 10.11.10, the POST /ClientLog/Document endpoint accepts the Authorization header's Client and Version fields and uses them unsanitized as components of the on-disk filename when persisting client-uploaded log documents. As a result, any authenticated non-admin user can include ../ sequences in the Client field to cause Jellyfin to write attacker-controlled content to arbitrary paths reachable by the Jellyfin service user, with a forced .log suffix. This vulnerability is fixed in 10.11.10.
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-2026-49247 has been found in Jellyfin.
Attackers can target a specific entry point like POST /ClientLog/Document over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 8.8/10.
What to do: upgrade Jellyfin to 10.11.10 or later.
If unsure, ask your IT team or search "Jellyfin CVE-2026-49247" on the vendor's site.
CVE-2026-49247 (Jellyfin) — CWE-22 / CVSS v3 8.8
Attack vector: remote (network-reachable) / no user interaction
Attack surface: POST /ClientLog/Document / Authorization header
Patched: 10.11.10 — apply immediately
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.
Path traversal (CWE-22) exists in Jellyfin. Attackers reach the vulnerable code path via POST /ClientLog/Document.
Check the vendor advisory for the affected versions of Jellyfin. Attack surface: POST /ClientLog/Document / Authorization header.
Severity: High (CVSS 8.8/10). Successful exploitation can lead to full system takeover.
Update to 10.11.10.
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 /ClientLog/Document 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 /ClientLog/Document' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
POST /ClientLog/Document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。 -
3Apply patch patch
Upgrade Jellyfin to 10.11.10ステージング環境で 10.11.10 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 2 で見つけた異常検知の続報チェックを含めること。
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4Post-deployment verification verify
Replay attack against POST /ClientLog/Document 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