Multiple vulnerabilities have been discovered in the libtiff library and the included tools, which may result in denial of service or the execution of arbitrary code.
For the oldstable distribution (jessie), these problems have been fixed in version 4.0.3-12.3+deb8u5.
For the stable distribution (stretch), these problems have been fixed in version 4.0.8-2+deb9u2.
Further information about Debian Security Advisories, how to apply these updates to your system and frequently asked questions can be found at: https://www.debian.org/security/