A libxdmcp security update has been released for Debian GNU/Linux 8 LTS

Package : libxdmcp
Version : 1:1.1.1-1+deb8u1
CVE ID : CVE-2017-2625

It has been found, that libxdmcp, an X11 Display Manager Control Protocol
library, uses weak entropy to generate keys.

Using arc4random_buf() from libbsd should avoid this flaw.

For Debian 8 "Jessie", this problem has been fixed in version
1:1.1.1-1+deb8u1.

We recommend that you upgrade your libxdmcp packages.

Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at: https://wiki.debian.org/LTS