pdf/pdf-write.c in Artifex MuPDF before 1.12.0 mishandles certain length changes when a repair operation occurs during a clean operation, which allows remote attackers to cause a denial of service (buffer overflow and application crash) or possibly have unspecified other impact via a crafted PDF document.
https://www.debian.org/security/2018/dsa-4334
https://bugs.ghostscript.com/show_bug.cgi?id=698699
http://www.ghostscript.com/cgi-bin/findgit.cgi?520cc26d18c9ee245b56e9e91f9d4fcae02be5f0