rsyslog librelp version 1.2.14 and earlier contains a Buffer Overflow vulnerability in the checking of x509 certificates from a peer that can result in Remote code execution. This attack appear to be exploitable a remote attacker that can connect to rsyslog and trigger a stack buffer overflow by sending a specially crafted x509 certificate.
https://www.debian.org/security/2018/dsa-4151
https://usn.ubuntu.com/3612-1/
https://security.gentoo.org/glsa/201804-21
https://lgtm.com/rules/1505913226124/
https://github.com/rsyslog/librelp/blob/532aa362f0f7a8d037505b0a27a1df452f9bac9e/src/tcp.c#L1205
https://access.redhat.com/errata/RHSA-2018:1707
https://access.redhat.com/errata/RHSA-2018:1704
https://access.redhat.com/errata/RHSA-2018:1703
https://access.redhat.com/errata/RHSA-2018:1702
https://access.redhat.com/errata/RHSA-2018:1701
https://access.redhat.com/errata/RHSA-2018:1225
https://access.redhat.com/errata/RHSA-2018:1223
http://packetstormsecurity.com/files/172829/librelp-Remote-Code-Execution.html