a NULL pointer dereference vulnerability located in the function select_value_catcher::setup at sql/opt_subselect.cc:6044

This is a NULL pointer dereference vulnerability in MariaDB located in the function select_value_catcher::setup at sql/opt_subselect.cc:6044. The function is called during the optimization of a semi-join involving a subquery, specifically in execute_degenerate_jtbm_semi_join(). The items parameter is nullptr, but the function assumes it is a valid pointer, leading to a segmentation fault. An attacker can trigger this by crafting a malicious UPDATE or SELECT query with certain semi-join patterns, resulting in a denial-of-service (DoS).