Stack-based buffer overflow in the parseLegacySyslogMsg function in tools/syslogd.c in rsyslogd in rsyslog 4.6.x before 4.6.8 and 5.2.0 through 5.8.4 might allow remote attackers to cause a denial of service (application exit) via a long TAG in a legacy syslog message.
imudp in rsyslog 4.x before 4.1.2, 3.21 before 3.21.9 beta, and 3.20 before 3.20.2 generates a message even when it is sent by an unauthorized sender, which allows remote attackers to cause a denial of service (disk consumption) via a large number of spurious messages.
The ACL handling in rsyslog 3.12.1 to 3.20.0, 4.1.0, and 4.1.1 does not follow $AllowedSender directive, which allows remote attackers to bypass intended access restrictions and spoof log messages or create a large number of spurious messages.