This vulnerability in Perl's S_measure_struct function involves an integer overflow that leads to an out-of-bounds heap read during pack and unpack operations. The function sums each item's size multiplied by its repeat count without overflow checks, causing the total size to wrap to a negative value when a large repeat count is used. The negative length comparison then incorrectly permits buffer pointer advancement beyond the allocated heap buffer, allowing a template derived from untrusted input to read memory beyond the intended buffer and return it to the caller. This affects numerous Ubuntu-distributed Perl versions up to 5.43.10.

An attacker able to supply crafted pack or unpack templates can exploit this vulnerability to read heap memory beyond the intended buffer boundaries. This can lead to disclosure of sensitive information from process memory. The vulnerability has a high impact on confidentiality, integrity, and availability as indicated by the CVSS vector (C:H/I:H/A:H), although no known exploits are reported in the wild at this time.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, avoid processing untrusted input with pack or unpack templates that could trigger the integer overflow. Monitor vendor channels for updates and apply patches promptly once released.