fast-xml-parser vulnerabilities

In fast-xml-parser versions 4.1.3 through before 5.3.5, a dot (.) in a DOCTYPE entity name is treated as a regex wildcard during entity replacement, allowing an attacker to shadow built-in XML entities (<, >, &, ", ') with arbitrary values. This bypasses entity encoding and leads to XSS when parsed output is rendered.

fast-xml-parser versions 5.9.3 through 5.10.1 have a vulnerability related to processing multiple DOCTYPE declarations in a single XML document. The addInputEntities() function resets entity expansion limits on each call, allowing bypass of protections and potentially causing excessive CPU usage, event-loop blocking, memory exhaustion, and process termination. The issue is fixed in version 5.10.1.

A vulnerability in the fast-xml-parser library allows a DoS attack via unlimited entity expansion. Even a small XML file can cause prolonged processing and freeze the application.

fast-xml-parser is an open source, pure JavaScript XML parser that allows special characters in entity names, which are not properly escaped. An attacker can exploit this vulnerability to perform denial of service (DoS) attacks by crafting entity names that generate inefficient regular expressions.