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.

YAML::Syck versions before 1.36 for Perl has missing null-terminators which causes out-of-bounds read and potential information disclosure Missing null terminators in token.c leads to but-of-bounds read which allows adjacent variable to be read The issue is seen with complex YAML files with a hash of all keys and empty values.  There is no indication that the issue leads to accessing memory outside that allocated to the module.