Create a table like this

CREATE TABLE `foo` (

  `id` int(11) NOT NULL,

  `modified` datetime NOT NULL,

  PRIMARY KEY (`id`)

);

Then run the following query to crash the server:

select a.* from foo a left join foo b on a.id = b.id where a.modified > b.modified or b.modified is null;

The query will enter the optimizing state and start consuming memory (and swap, if applicable) until the server runs out of memory and mysqld is killed.

Note that it does not matter whether the table is an InnoDB or MyISAM table. MySQL 5.5.29 does not exhibit this behavior.