CVE-2026-57076 is a heap use-after-free vulnerability in YAML::Syck versions prior to 1.47 for Perl. The issue arises because an anchor name allocated by syck_strndup is stored both as node->anchor and as a key in the parser's anchors table. When the node is freed, the shared key is also freed, but a subsequent anchor redefinition causes the anchors table to compare against this freed key, resulting in a read of freed heap memory. This vulnerability is reachable on the default Load path without special flags, affecting any caller that processes untrusted YAML documents with anchor redefinitions.

The vulnerability allows reading of freed heap memory during YAML parsing, which can lead to undefined behavior including potential crashes or memory corruption. Since anchors are a standard YAML feature and no special flags are needed to trigger this, any application using vulnerable YAML::Syck versions to load untrusted documents is at risk of memory safety issues.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, avoid loading untrusted YAML documents that redefine anchors using vulnerable versions of YAML::Syck. Monitor vendor channels for updates or patches addressing this issue.