Golden rule is the darker the malt, the more it can withstand moisture. Crystal malts are more forgiving than base malt. I remember trying out of date wheat malt and was not impressed. Strange funk and even the mash looked funny. Mind you you probably wont be using much caragold.
Inspect the malt. See how it looks, anything off? Have a taste, just chew it in your mouth. It should generate a predominently sweet taste in your mouth. If there are no off flavours you might think why not.
However, if the bag is tiny in the first place, a new one really cheap and you live next to a homebrew shop then you may instead decide to have a zero compromise policy to your ingredients. It is six months out of date.