/usr/share/ghostscript/9.26/Resource/CIDFSubst/DroidSansFallback.ttf is in libgs9-common 9.26a~dfsg-0+deb9u1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/ghostscript/9.26/Resource/CIDFSubst/../../../../fonts/truetype/droid/DroidSansFallbackFull.ttf