libebml before 1.3.6, as used in the MKV module in VideoLAN VLC Media Player binaries before 3.0.3, has a heap-based buffer over-read in EbmlElement::FindNextElement.
https://usn.ubuntu.com/4073-1/
https://trac.videolan.org/vlc/ticket/22474
https://github.com/Matroska-Org/libebml/compare/release-1.3.5...release-1.3.6
https://github.com/Matroska-Org/libebml/commit/b66ca475be967547af9a3784e720fbbacd381be6
https://github.com/Matroska-Org/libebml/commit/05beb69ba60acce09f73ed491bb76f332849c3a0