The ClamAV AntiVirus software versions 0.99.2 and prior contain a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to a lack of input validation checking mechanisms during certain mail parsing functions (the rfc2047 function in mbox.c). An unauthenticated, remote attacker could exploit this vulnerability by sending a crafted email to the affected device. This action could cause a buffer overflow condition when ClamAV scans the malicious email, allowing the attacker to potentially cause a DoS condition on an affected device.
https://usn.ubuntu.com/3550-2/
https://usn.ubuntu.com/3550-1/
https://lists.debian.org/debian-lts-announce/2018/01/msg00035.html
http://blog.clamav.net/2018/01/clamav-0993-has-been-released.html