CVE-2026-19913: high-severity vulnerability in Kaltura HTML5 Video Player, html5lib library

The Kaltura HTML5 player (mwEmbed / html5lib) contains a local file disclosure vulnerability due to improper validation of the ServiceUrl parameter in mwEmbedLoader.php. This parameter is used as the base URL for a backend request and accepts non‑HTTP schemes such as file://. When an exception or error occurs, the response is subsequently deserialized and its raw contents are reflected to the client in an error message; this enables an unauthenticated, remote attacker to read any arbitrary internal file reachable by the server. Affected versions include html5lib v2.45, v2.103 and earlier, and other v2.x releases exposing the vulnerable endpoint.