The KaxInternalBlock::ReadData function in libMatroska before 1.4.4 allows context-dependent attackers to obtain sensitive information from process heap memory via crafted EBML lacing, which triggers an invalid memory access.
https://github.com/Matroska-Org/libmatroska/commit/0a2d3e3644a7453b6513db2f9bc270f77943573f
https://github.com/Matroska-Org/libmatroska/blob/release-1.4.4/ChangeLog
http://www.debian.org/security/2016/dsa-3526
http://lists.opensuse.org/opensuse-updates/2016-01/msg00035.html
http://lists.matroska.org/pipermail/matroska-users/2015-October/006985.html