There’s a possible buffer overflow in OpenSSH prior to 3.7.1. Now, if security is a concern, even if it’s improbable that this might affect you, I urge you to stay proactive in your system’s maintenance!
I’ve written up a small HOWTO, available via my diary (link here), which gives a fairly brief, yet functional overview for how I compiled OpenSSH 3.7.1p1 for MacOS X, and got it to work.
Please note that this requires the Developer Toolkit, and a general familiarity with UNIX in general.
(As a side note, if you use sendmail; look here for information on a new issue.)
[Edit: URL updated since diary functionale integrated into primary system]