XML::Parser versions through 2.47 for Perl has an off-by-one heap buffer overflow in...

XML::Parser versions through 2.47 for Perl has an off-by-one heap buffer overflow in st_serial_stack.

In the case (stackptr == stacksize - 1), the stack will NOT be expanded. Then the new value will be written at location (++stackptr), which equals stacksize and therefore falls just outside the allocated buffer.

The bug can be observed when parsing an XML file with very deep element nesting