CVE-2026-19913
Description
A flaw was found in the Kaltura HTML5 player (mwEmbed / html5lib). An unauthenticated, remote attacker can exploit improper validation of the ServiceUrl parameter in mwEmbedLoader.php. This parameter, used for backend requests, accepts non-HTTP schemes such as file://. When an exception or error occurs, the response is deserialized and its raw contents are reflected to the client, allowing the attacker to read arbitrary internal files on the server. This leads to information disclosure.
Statement
CVE-2026-19913 is an SSRF vulnerability that affects the Kaltura HTML5 Player (a PHP media component utilizing a library also called 'html5lib'). It is completely unrelated to the 'python-html5lib' (Python HTML parser) or 'python-bleach' packages shipped by Red Hat.
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data
Integrity
Technical Impact: Execute Unauthorized Code or Commands
Access Control
Technical Impact: Bypass Protection Mechanism
By providing URLs to unexpected hosts or ports, attackers can make it appear that the server is sending the request, possibly bypassing access controls such as firewalls that prevent the attackers from accessing the URLs directly. The server can be used as a proxy to conduct port scanning of hosts in internal networks, use other URLs such as that can access documents on the system (using file://), or use other protocols such as gopher:// or tftp://, which may provide greater control over the contents of requests.
Frequently Asked Questions
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