VU#308749: Remote Code Execution and Arbitrary File Read Vulnerabilities in Kaltura Servers

Overview

The Kaltura HTML5 Player V2 Library (mwEmbed / html5lib) contains two vulnerabilities, both involving the same insecure deserialization flaw, that enable arbitrary file read and remote code execution. Affected versions include html5lib v2.45, v2.103 and earlier, and other v2.x releases that expose the vulnerable mwEmbedLoader.php endpoint. Notably, only versions of the legacy player (Player V2) are vulnerable; these issues do not affect any versions of the currently supported Kaltura Player V7.

Description

Kaltura is an AI video platform that provides tools for video management, publishing, playback, and integration with web applications. Kaltura’s HTML5 player library exposes the mwEmbedLoader.php endpoint, which accepts a user-controlled ServiceUrl parameter as the target URL for backend API requests. The KalturaClientBase PHP client library fetches data from this URL and automatically deserializes it using PHP's unserialize() function without validating source, scheme, or content.

CVE-2026-19913 results from the combination of this unsafe deserialization flaw and improper error-handling behavior. An attacker can provide the location of a local file to ServiceUrl as a file:// path, and the client will fetch the internal file's contents and attempt to deserialize them. When deserialization fails, the raw bytes are reflected back to the client in the resulting error message, enabling the attacker to read any file accessible to the web-server user.