The remote Debian host is missing a security-related update.
Multiple heap buffer over reads were discovered in freexl, a library to read Microsoft Excel spreadsheets, which could result in denial of service.
Upgrade the freexl packages. For the oldstable distribution (jessie), these problems have been fixed in version 1.0.0g-1+deb8u5. For the stable distribution (stretch), these problems have been fixed in version 1.0.2-2+deb9u2.