DNS dissector in Ethereal before 0.9.3 allows remote attackers to cause a denial of service (CPU consumption) via a malformed packet that causes Ethereal to enter an infinite loop.
Multiple buffer overflows in AFS ACL parser for Ethereal 0.8.13 and earlier allows remote attackers to execute arbitrary commands via a packet with a long username.
tcpdump, Ethereal, and other sniffer packages allow remote attackers to cause a denial of service via malformed DNS packets in which a jump offset refers to itself, which causes tcpdump to enter an infinite loop while decompressing the packet.