Is it safe to cook wine or vinegar in cast iron?
I'd like to refer you to my answer to the question about chili in cast iron, from which I'll summarize the relevant parts:


Typical cast iron corrodes at a pH lower than 4.3; pure white vinegar (5%) has a pH of 2.4 and wine is around 3.2 to 3.8.  If you plan to use either of these in cast iron, you'd better make sure they are heavily diluted, otherwise you may actually ruin your pot in addition to getting a pretty hefty iron supplement with your meal.
Cast iron is still somewhat reactive at borderline pH ranges, i.e. tomato juice or sauce.  It'll leach out about 5 mg of iron for every 3 oz / 88 mL of liquid for typical cooking times.  The typical human needs to ingest significantly more than 45 mg over a period of several days to become toxic, so it's generally considered OK and even healthy to cook dilute tomato solutions in cast iron, but wine and vinegar are another story.


Don't fill your cast-iron cookware with wine or vinegar.  A splash for sauce or deglazing is OK, but tossing a significant amount straight into the pan undiluted will ruin your cookware, and your health.

P.S. Note that enameled cast iron (Le Creuset, etc.) is less reactive; the specifics depend on the brand.  If you have this type of cast iron, I suggest doing your homework before taking the risk.