[Dovecot] segfault - (imap|pop3)-login during nessus scan

[Todd Rinaldo]

We've been struggling with a problem for the past couple of days which to this point I've only gotten to be able to boil down to this:

1. Install nessus home edition (less pluggins I assume)
2. run all scans (sequentially or in parallel, doesn't seem to matter)
3. about 3 minutes in /var/log/messages will show segfaults on imap and/or pop3

imap-login[22185]: segfault at 000000000000000c rip 0000003c7de610a2 rsp 00007fffa2342068 error 4
or sometimes...
pop3-login[24451]: segfault at 000000000000000c rip 0000003c7de610a2 rsp 00007fff07116968 error 4

I'm having a really hard time getting a core dump and I'm having a really hard time narrowing down the list of nessus tests which cause this. So far, I have repeated this failure in 1.1.19 and 1.1.20

Additionally we've seen something similar on 1.2 and reverted back to 1.1 a year ago. At the time we could not re-produce a test case and finally gave up.

Has anyone seen something along these lines? 

Can anyone recommend how I could narrow this down further so we can find the problem?

Thanks,
Todd