http://kb.parallels.com/en/111296 says:



If you're using Postfix with Plesk then Cyrus SASL support gets enabled.

According to https://bugzilla.redhat.com/show_bug.cgi?id=699035 EL4-6 are also affected, but an update that fixes this is not available yet.

More links:

http://www.postfix.org/CVE-2011-1720.html
http://thread.gmane.org/gmane.mail.postfix.announce/127

Thanks for alerting everyone. So I've been talking to the kernel guys about this, and the ASL kernel should protect you from this being exploitable (it may not even be exploitable).

Also, if postfix is chrooted (it is in some environments) then all the chroot-related options will help to contain any potential compromise as well if you were not running an ASL kernel (again, with an ASL kernel this is not likely to be exploitable, if it even is, anyway). Not sure if thats the case with Plesk though.

As always though we recommend you patch your systems, this is a bug too and it may effect reliability of the software. And defense in depth is a good idea, so even though the kernel may protect you, we still recommend you patch to protect reliability and to give you more defense in depth.

An update for RHEL/CentOS which fixes this is available: https://rhn.redhat.com/errata/RHSA-2011-0843.html