I doesn't have understeer as such, but if you've not got your wheel set up properly, or in some cases can't, such as some Logitech users (like me), then a problem you do have is a lack of confidence in what the car is doing. The front-end you can see, it's the back end that is less obvious, so it makes you feel like you're oversteering. It's the much commented on lack of feel, but once you've done a good bit of driving you don't really notice it, until you do some consistant running in another sim (going from rF to GTP you can really see the difference).
But yeah, the default setups understeer a good bit - less so than most default setups on other games, but it's there non-the-less.
To get more feel in the F3 mod add some negative camber. The default settings have no camber at all.