Perl Out-of-bounds Read Vulnerability - CVE-2026-57432

Perl versions through 5.43.10 have an integer overflow in S_measure_struct leading to an out-of-bounds heap read in pack and unpack. S_measure_struct adds each item39s size times its repeat count to a running total with no overflow check so a large repeat count in a pack or unpack template wraps the signed SSize_t total negative. The X and x position codes then guard their moves with a signed length comparison that passes when the length is negative advancing the buffer pointer out of bounds. A template derived from untrusted input can read heap memory past the buffer and return it to the caller.