The remote Debian host is missing a security-related update.
It was discovered that various procedures in Ghostscript, the GPL PostScript/PDF interpreter, do not properly restrict privileged calls, which could result in bypass of file system restrictions of the dSAFER sandbox.
Upgrade the ghostscript packages. For the oldstable distribution (stretch), these problems have been fixed in version 9.26a~dfsg-0+deb9u5. For the stable distribution (buster), these problems have been fixed in version 9.27~dfsg-2+deb10u2.