Fix four libsyck memory-safety CVEs reachable from the default YAML::Syck::Load() path on untrusted input with no special flags (reported by Paul Johnson via CPANSec, PR #213):
CVE-2026-57075 (CWE-125): out-of-bounds read in the base64 decoder caused by signed-char indexing of the decode table on !!binary input
CVE-2026-57076 (CWE-416): use-after-free of an anchor key string shared between the node and the anchors table
CVE-2026-57077 (CWE-125): one-byte out-of-bounds read in the lexer newline scan during block-scalar parsing (incomplete-fix follow-on to CVE-2025-11683)
CVE-2026-13713 (CWE-416/CWE-415): use-after-free / double-free of an anchor node on anchor redefinition, a remote-crash DoS from a 7-byte input
Harden syck_base64dec() to bounds-check each read so it cannot run past a non-NUL-terminated input buffer (defense-in-depth for callers passing raw buffers; PR #213)
Bug Fixes
Fix: enforce $MaxDepth on Load to prevent C-stack exhaustion from deeply nested YAML/JSON input; YAML::Syck and JSON::Syck Load now default to 512, matching Dump (PR #204)
Fix: emit YAML canonical forms (.nan, .inf, -.inf) for NaN/Inf values in Dump so they roundtrip with ImplicitTyping instead of reloading as plain strings (PR #201)
Maintenance
CI: add an AddressSanitizer job that builds the XS with -fsanitize=address and runs the suite plus the CVE trigger inputs to catch libsyck memory-safety defects; de-pin the libasan version so it tracks the runner's GCC (PR #213)