The vulnerability in YAML::Syck (before version 1.47) arises from improper memory management in the bundled libsyck library. When an anchor name is redefined or removed, the associated node is freed while it may still reside on the parser's value stack. Subsequent parser operations attempt to free this node again, causing a double-free and use-after-free condition. This leads to interpreter aborts and crashes during the Load or LoadFile operations on maliciously crafted YAML documents containing anchor redefinitions.

This vulnerability causes a denial of service by crashing the Perl interpreter when processing specially crafted YAML documents that redefine anchors during parsing. There is no indication of code execution or data corruption beyond the interpreter crash. No known exploits are reported in the wild.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, avoid parsing untrusted YAML documents that redefine anchors mid-parse to prevent interpreter crashes.