The check_connection function in sql_parse.cc in MySQL 4.0.x up to 4.0.26, 4.1.x up to 4.1.18, and 5.0.x up to 5.0.20 allows remote attackers to read portions of memory via a username without a trailing null byte, which causes a buffer over-read.

Buffer overflow in the open_table function in sql_base.cc in MySQL 5.0.x up to 5.0.20 might allow remote attackers to execute arbitrary code via crafted COM_TABLE_DUMP packets with invalid length values.

MySQL 5.0.18 and earlier allows local users to bypass logging mechanisms via SQL queries that contain the NULL character, which are not properly handled by the mysql_real_query function. NOTE: this issue was originally reported for the mysql_query function, but the vendor states that since mysql_query expects a null character, this is not an issue for mysql_query.