The SwCTBWrapper::Read function in sw/source/filter/ww8/ww8toolbar.cxx in LibreOffice before 5.4.6.1 and 6.x before 6.0.2.1 does not validate a customizations index, which allows remote attackers to cause a denial of service (heap-based buffer overflow with write access) or possibly have unspecified other impact via a crafted document that contains a certain Microsoft Word record.
https://www.libreoffice.org/about-us/security/advisories/cve-2018-10120/
https://www.debian.org/security/2018/dsa-4178
https://usn.ubuntu.com/3883-1/
https://lists.debian.org/debian-lts-announce/2018/04/msg00021.html
https://gerrit.libreoffice.org/#/c/49500/
https://gerrit.libreoffice.org/#/c/49499/
https://gerrit.libreoffice.org/#/c/49486/