Heap-based buffer overflow in dns.cpp in InspIRCd 2.0.5 might allow remote attackers to execute arbitrary code via a crafted DNS query that uses compression.
InspIRCd 3.8.0 through 3.9.x before 3.10.0 allows any user (able to connect to the server) to access recently deallocated memory, aka the "malformed PONG" issue.