That's the good news. The bad news is, it's still affected by CVE-2007-5925, which allows remote authenticated users to cause a denial of service (database crash). Jörg Brühe wrote on the packagers mailinglist that's because the sources for 5.0.51 were cloned before the fix got in. I don't know exactly how their release model works, but looks like it needs to be improved.
To make it even worse, bug #32125 which has a patch for the problem, was set to private a few days ago. Because we already have the patch in our MySQL packages since exactly three weeks, it's available in our subversion repository.