Bug#983684: mupdf: CVE-2021-3407

[Bastian Germann]

On Sun, 28 Feb 2021 13:33:23 +0100 Salvatore Bonaccorso 
<car...@debian.org> wrote:
CVE-2021-3407[0]:
| A flaw was found in mupdf 1.18.0. Double free of object during
| linearization may lead to memory corruption and other potential
| consequences.

See #983104 for a NMU RFS with the fix for buster.