CVE-2026-57075: Toddr Yaml::syck

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

YAML::Syck versions before 1.47 for Perl allow an out-of-bounds read via a signed-char lookup-table index in syck_base64dec. The base64 decoder in the bundled libsyck indexes the 256-entry static table b64_xtable with a signed char, so any !!binary byte >= 0x80 sign-extends to a negative index and reads before the table. The decoder receives the raw bytes of any !!binary node, a standard YAML type not gated by $LoadBlessed or $LoadCode, so it is reached on the default Load path. Any caller that runs Load or LoadFile on an untrusted document containing a !!binary scalar with a high-bit byte triggers the read, and the value read can surface in the decoded result.

Affected products

• Toddr Yaml::syck: before 1.47 (fixed in 1.47)

Published 2026-07-16. Last modified 2026-07-17.