CVE-2026-49247: Jellyfin

High severity, CVSS 8.8. EPSS: 0.5% chance of exploitation in the next 30 days.

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.

Affected products

• Jellyfin Jellyfin: from 10.9.0, before 10.11.10 (fixed in 10.11.10)

Published 2026-06-24. Last modified 2026-06-26.