In PHP versions:8.1.* before 8.1.34, 8.2.* before 8.2.30, 8.3.* before 8.3.29, 8.4.* before 8.4.16, 8.5.* before 8.5.1, a heap buffer overflow occurs in array_merge() when the total element count of packed arrays exceeds 32-bit limits or HT_MAX_SIZE, due to an integer overflow in the precomputation of element counts using zend_hash_num_elements(). This may lead to memory corruption or crashes and affect the integrity and availability of the target server.
https://lists.debian.org/debian-lts-announce/2026/01/msg00019.html
https://github.com/php/php-src/security/advisories/GHSA-h96m-rvf9-jgm2
Published: 2025-12-27
Updated: 2026-01-24
Base Score: 8.5
Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:P/A:C
Severity: High
Base Score: 8.2
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Severity: High
Base Score: 8.3
Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
Severity: High
EPSS: 0.0004