ClamAV is a GPL virus scanner.
ClamAV contains format string vulnerabilities in the logging code (CVE-2006-1615). Furthermore Damian Put discovered an integer overflow in ClamAV's PE header parser (CVE-2006-1614) and David Luyer discovered that ClamAV can be tricked into performing an invalid memory access (CVE-2006-1630).
By sending a malicious attachment to a mail server running ClamAV, a remote attacker could cause a Denial of Service or the execution of arbitrary code. Note that the overflow in the PE header parser is only exploitable when the ArchiveMaxFileSize option is disabled.
There is no known workaround at this time.
All ClamAV users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=app-antivirus/clamav-0.88.1"