Uncontrolled recursion vulnerability in the RelaxNG include handling logic of the libxml2 XML parsing library. The issue arises from the absence of limits on recursive <include> directive resolution. When a deeply nested chain of included RelaxNG schema files is processed, the parser enters unbounded recursion, eventually exhausting the system call stack. This results in a stack overflow and application crash. Exploitation requires attacker-controlled schema input and primarily impacts availability by causing a denial of service.