Coming up with the exact number is likely to be very difficult but i would put it in the range of 1-2 minutes to impossible.
Let's ignore the lack of oxygen and assume you could hold your breath long enough to reach the safe haven.
The extreme cold would easily drop your core temperature to the realm of severe hypothermia within minutes.
If that doesn't kill you first then the extreme cold has already caused your blood vessels to shrink before you can even take more than a few steps. On top of this the extreme cold is enough to freeze solid any muscles and other tissue, making movement painful / difficult / impossible.
Now lets assume that through some miracle none of that kills you and you make it to the safe haven. The distinct lack of a magnetic field around the planet exposes you to high levels of UV radiation. Being completely naked and having your entire body exposed to this level of UV is likely to cause lots of mutations throughout your cells. Which in itself will kill you.
So your chances aren't looking good for anything beyond a minute!