How to fix the OS X Server "LibClamAV Error: mpool_malloc(): Attempt to allocate 8388608 bytes." reboot loop?
I ran across this page dealing with the issue on a carefully rebuilt OS X server running 10.6 (I have reasons). The compile-it-yourself answer by Pro Backup is fantastically detailed, but I may have run across a simpler answer, at least in the short term. I noticed another machine I had, also using 10.6 Server, didn't have the issue. Checking the versions of each using /usr/bin/clamscan --version, I saw they were the same engine versions, but different definition versions:

Has the issue

ClamAV 0.97.8/22421/Sun Oct 23 22:58:38 2016
ClamAV 0.97.8/22422/Mon Oct 24 12:02:38 2016


versus

Doesn't have the issue

ClamAV 0.97.8/22470/Wed Nov  2 19:05:24 2016


Manual download clamAV definitions

So, decided to try manually downloading the virus definitions using /usr/bin/freshclam (as sudo). It ran through lots of versions, finishing with 22471. Not yet sure if this will do the trick, but I'm hoping it's on the right track.