net-snmp was found to be crashing/hanging due to the heavy load on the subagent AgentX.
Here, snmpd is the master agent, AgentX is the subagent registering to handle a MIB and processing GETNEXT requests. When the subagent is under heavy load, requests start to pile up in the queue, replies from the subagent arrive too late (per log messages) and eventually the subagent is timed out. When the timeout occurs there is a high probability of either a crash (Segfault) or a hang (100% CPU utilisation, tight loop in the snmpd code) dependent on the version of the snmpd under test. This also happens when the subagent dies unexpectedly with outstanding transactions unserviced.
Created net-snmp tracking bugs for this issue:
Affects: fedora-all [bug 1038011]
net-snmp-5.7.2-13.fc19 has been pushed to the Fedora 19 stable repository. If problems still persist, please make note of it in this bug report.
net-snmp-5.7.2-7.fc18 has been pushed to the Fedora 18 stable repository. If problems still persist, please make note of it in this bug report.
net-snmp-5.7.2-16.fc20 has been pushed to the Fedora 20 stable repository. If problems still persist, please make note of it in this bug report.
This issue was corrected in Red Hat Enterprise Linux 6 via RHBA-2013:1150
before it was considered a security flaw.
The upstream patch is here:
Created attachment 870332 [details]
And I've just checked that this patch fixes the bug.
Created attachment 870333 [details]
I accidentally attached wrong patch, this is the right one.
This issue has been addressed in following products:
Red Hat Enterprise Linux 5
Via RHSA-2014:0322 https://rhn.redhat.com/errata/RHSA-2014-0322.html