The remote host is vulnerable to a buffer overflow.
The remote host is running ClamAV, an open-source antivirus solution for Unix-like systems. This version of ClamAV is reported to be vulnerable to a flaw where the parsing of a malicious file will cause the clamav process to overflow system memory, possibly resulting in an attacker executing code. An attacker exploiting this flaw would need to be able to send a specially formed email to the system running ClamAV.
Upgrade to version 0.86.2 or higher.