Did you update your console to OFW 3.6x+? if yes, then you can't
else, you might have a spoofer installed on your PS3, thus it will result that your PS3 will report that your on "x.xx" firmware version, although you are actually in 3.55 CFW.
My suggestion is, do not take any CFW install higher than 3.55, "there is no such CFW in 3.60, 3.70, 4.00, 4.11, 4,21 , etc...." if you want to update.
I don't know what kind of update you want but, there are no updates on CFW since Last February 2011 we're KMEAW CFW with the most important feature "peek/poke" was ported that will enable us to load the payload such as SC-36 or SC-8 which is important for backup loading, there's no updates more than that. Although REBUG firmware had such update system on CFW, which is pretty much easy to do by just installing a pkg and executing that installed pkg.
But if you ask that if you can update to latest CFW, if it happens there is. Well, yes you can. Just go to recovery mode and install the latest pup file there. Also dont forget to disable your spoofer or else, you cant install anything.