CVE-2026-4177: Toddr Yaml::syck

Critical severity, CVSS 9.1. EPSS: 0.6% chance of exploitation in the next 30 days.

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.

Affected products

• Toddr Yaml::syck: before 1.37 (fixed in 1.37)

Published 2026-03-16. Last modified 2026-07-15.