Security researchers have discovered a vulnerability in Apple's popular iTunes application which might be exploited to interfere with shared music downloads.

The glitch in iTunes 6.x - involving a failure to authenticate the source of shared music lists received via multicast - is currently unpatched. So it's just as well that it's described by the man who discovered the flaw, Seth Fogie of Airscanner, as annoying rather than potentially devastating.

iTunes Shared Music allows users to create playlists for songs on their PC and to share them across a network, a function that only works if copy protection restrictions are absent.

The vuln (Airscanner advisory and Flash demo here) might be exploited to kill an existing stream without authorisation via an anonymous packet. At worst the glitch might also permit the Shared Music lists from various users to be renamed and swapped, thus creating a chaotic environment. These avenues of attack exist because it's possible to create spoofed Shared Music entries, to rename existing entries, to disconnect existing entries and to re-initiate existing lists.

Version 6.0 of iTunes on Win XP and OS X have been confirmed as vulnerable. Other versions may also be affected. There's no fix, as yet, so it's just as well the glitch is classified as low risk. Security notification firm Secunia advises iTunes users to restrict their use of the shared music feature to within trusted networks only, as a precaution. Airscanner advises users to disable the 'look for shared music' option under the Sharing tab in Preferences. ®