5.8 has only just been released. I quote from the CentOS mailing list:
Date: Mon, 05 Mar 2012 04:12:01 -0600
From: Johnny Hughes <firstname.lastname@example.org>
Subject: Re: [CentOS] CentOS 5.8 Critical Samba Update
I am populating the CentOS mirrors with the 5.8 release at this time.
We are very close to releasing 5.8, just doing some extended testing,
which I fully expect it to pass based on the fixes rolled in.
I expect that CentOS-5.8 will be released to the external mirrors in
less than 24 hours and released to the 24-48 hours after that.
So, look for 5.8 to be released in the next 24-72 hours.
Depending on how frequently and at what time of day your currently-preferred mirror resyncs, there can be a delay while the new binaries propagate around the whole mirror network; the mirrors that happened to resync at the right time will have them, while those that are waiting for their next resync won't.
If this annoys you, I have found that a
yum clean all will often allow me to randomly pick a different mirror, and that may have the updates ready to go.
If it really annoys you, you should look through the mirrors listed in the CentOS mirror list, find one that's close to you and that has the updates, and hardwire it into your
Or you could just wait another day or two!