Damian Lukowski discovered a flaw in spamassassin, a Perl-based spam filter using text analysis. Malicious rule configuration files, possibly downloaded from an updates server, could execute arbitrary commands under multiple scenarios.
For Debian 8 jessie, these problems have been fixed in version 3.4.2-0+deb8u4.
We recommend that you upgrade your spamassassin packages.
Further information about Extended LTS security advisories can be found at: https://deb.freexian.com/extended-lts/