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.

• https://github.com/cpan-authors/YAML-Syck/pull/65
• https://metacpan.org/dist/YAML-Syck/changes

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.

• https://github.com/cpan-authors/YAML-Syck/commit/e8844a31c8cf0052914b198fc784ed4e6b8ae69e.patch
• https://metacpan.org/release/TODDR/YAML-Syck-1.37_01/changes#L21
• http://www.openwall.com/lists/oss-security/2026/03/16/6