CVE-2026-49220
Description
Jellyfin is an open source self hosted media server. Prior to 10.11.9, a potential XSS attack exists in Jellyfin which can allow a non-privileged user to execute arbitrary Javascript in the context of a logged-in Administrative user, resulting in numerous potential issues. The Client header during an AuthenticateByName can contain arbitrary HTML and Javascript, which will then be executed by the Administrative user when visiting the Access tab of the user in question from within the dashboard. This vulnerability is fixed in 10.11.9.
Summary dbcve.org
A stored XSS vulnerability exists in Jellyfin where a non-privileged user can inject arbitrary HTML and JavaScript via the Client header during the AuthenticateByName process. This malicious payload executes when an Administrative user views the Access tab of the compromised user from the Jellyfin dashboard, allowing the attacker to run code in the admin's session context.
Mitigation
Upgrade Jellyfin to version 10.11.9 or later. As a temporary measure, administrative users should avoid accessing user Access tabs from untrusted sources until the patch is applied.