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
Fixed bug reported by Enno Derksen <enno@att.com>: Now treats parameter entity declarations correctly. The entity handler sees the name beginning with '%' if it's a parameter entity declaration.
Nigel Hutchison <nwoh@software-ag.de> pointed out that stream.t wasn't portable off Unix systems. Replaced with portable version.
Fixed bug reported by Enno Derksen <enno@att.com>: XML Declaration was firing off both XMLDecl handler *and* Default handler.
Added option NoExpand to Expat to turn off expansion of entity references when a default handler is set.