demux/mkv/mkv.hpp in the MKV demuxer plugin in VideoLAN VLC media player 1.1.6.1 and earlier allows remote attackers to cause a denial of service (crash) and execute arbitrary commands via a crafted MKV (WebM or Matroska) file that triggers memory corruption, related to "class mismatching" and the MKV_IS_ID macro.
The StripTags function in (1) the USF decoder (modules/codec/subtitles/subsdec.c) and (2) the Text decoder (modules/codec/subtitles/subsusf.c) in VideoLAN VLC Media Player 1.1 before 1.1.6-rc allows remote attackers to execute arbitrary code via a subtitle with an opening "<" without a closing ">" in an MKV file, which triggers heap memory corruption, as demonstrated using refined-australia-blu720p-sample.mkv.