The remote host is missing an update to clamav announced via advisory DSA 1366-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201366-1

Several remote vulnerabilities have been discovered in the Clam anti-virus toolkit. The Common Vulnerabilities and Exposures project identifies the following problems: CVE-2007-4510 It was discovered that the RTF and RFC2397 parsers can be tricked into dereferencing a NULL pointer, resulting in denial of service. CVE-2007-4560 It was discovered clamav-milter performs insufficicient input sanitising, resulting in the execution of arbitrary shell commands. The oldstable distribution (sarge) is only affected by a subset of the problems. An update will be provided later. For the stable distribution (etch) these problems have been fixed in version 0.90.1-3etch7. For the unstable distribution (sid) these problems have been fixed in version 0.91.2-1. We recommend that you upgrade your clamav packages.