Not common but like any other rubber thing secured by a clamp a leak can occur.
Needless to say the clamps are not sold separately, you are expected to put your hand in your pocket and cough some huge, usurious amount, (Really, a large lump of change!) for a new boot and clamps and probably *Special* pliers to install same.
Thing is as long as the boot itself is uncompromised you can go to 'Wottalottacrap Auto' and buy yourself a CV boot clamp, (Buy several, you'll probably fuck the first one getting the hang of it.) and the tool to install them properly. That will probably cost you about $30.
Pry off and discard the original clamp, (The one at the bottom of the boot where I assume the leak is occurring?) and pull the boot up to examine it and the surface it clamps on. Give it a clean and smear a bit of Threebond 1211 or some other gasket snot around the clamping surface of the casting. Pop the boot back down over the casting and use your newly acquired boot clamp tool and clamp to tighten the clamp down 'Till you fart' tight. I usually use long clamps and go around twice, this effectively doubles the clamping force. The tool has a cut-off feature you use after you've doubled the clamp back on itself. Peen the end of the clamp down and lock it with the tangs. Roll the outer lip of the boot down over the clamp. Job done.
Before you do that though remove the shitty breather tower and make sure its clear otherwise the box will tend to pressurise. That may be causing the leak.