XML::Parser versions through 2.45 for Perl could overflow the pre-allocated buffer size cause a heap corruption (double free or corruption) and crashes. A :utf8 PerlIO layer, parse_stream() in Expat.xs could overflow the XML input buffer because Perl's read() returns decoded characters while SvPV() gives back multi-byte UTF-8 bytes that can exceed the pre-allocated buffer size. This can cause heap corruption (double free or corruption) and crashes.

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

YAML::Syck versions through 1.36 for Perl has several potential security vulnerabilities including a high-severity heap buffer overflow in the YAML emitter. The heap overflow occurs when class names exceed the initial 512-byte allocation. The base64 decoder could read past the buffer end on trailing newlines. strtok mutated n->type_id in place, corrupting shared node data. A memory leak occurred in syck_hdlr_add_anchor when a node already had an anchor. The incoming anchor string 'a' was leaked on early return.