A security issue and vulnerability have been reported in MySQL
An error when verifying authentication attempts can be exploited to bypass the authentication mechanism.
Successful exploitation of this vulnerability requires MySQL to be built on a system with a library that allows "memcmp()" to return a value outside of the -128 through 127 range (e.g. sse-optimized glibc). NOTE: Vendor binaries are reportedly not affected.
The security issue is reported in versions prior to 5.1.63 and 5.5.25.
Update to version 5.1.63 or 5.5.25.