CVE-2026-7259 Null pointer dereference in php_mb_check_encoding() via mb_ereg_search_init()

In PHP versions 8.2. before 8.2.31, 8.3. before 8.3.31, 8.4. before 8.4.21, and 8.5. before 8.5.6, a mismatch between encoding lists in Oniguruma and mbfl leads to a NULL pointer dereference, resulting in a segmentation fault and denial of service. The vulnerability is exploitable when...