Brad Pitt is threatening legal action against Vanity Fair magazine for using a picture of him dressed -- or undressed -- in boxer shorts and white socks on the cover of its December issue. Pitt claims that he never authorized publication of the picture, which was taken by photographer Robert Wilson as part of a video art project last year. As reported by the London Independent, the magazine used the Pitt photo in connection with an art feature about Wilson. Vanity Fair said that Pitt had signed a photo release agreeing to allow the photographer to use any image of him that Wilson had taken in connection with publicity for the video project. Moreover, it said, it sent Pitt a letter dated Oct. 5, 2006 informing him that the picture was going to be featured on the cover of Vanity Fair.