Description
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 item's 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.
Problem types
CWE-190 Integer Overflow or Wraparound
Product status
Any version
References
www.openwall.com/lists/oss-security/2026/07/13/6
github.com/...5f7eb6bbbe0510964e3fb1d6bb691e5445913e55.patch
github.com/...40754edc72dd3e513d758153c0e2f0215897740e.patch