Rainer Gerhards, the rsyslog project leader, reported a vulnerability in Rsyslog, a system for log processing. As a consequence of this vulnerability an attacker can send malformed messages to a server, if this one accepts data from untrusted sources, and trigger a denial of service attack.
For the stable distribution (wheezy), this problem has been fixed in version 5.8.11-3+deb7u1.
For the unstable distribution (sid), this problem has been fixed in version 8.4.1-1.
We recommend that you upgrade your rsyslog packages.