Buffer overflow in the RPC preprocessor for Snort 1.8 and 1.9.x before 1.9.1 allows remote attackers to execute arbitrary code via fragmented RPC packets.

Snort 1.8.3 does not properly define the minimum ICMP header size, which allows remote attackers to cause a denial of service (crash and core dump) via a malformed ICMP packet.

Unknown vulnerability in IP defragmenter (frag2) in Snort before 1.8.3 allows attackers to cause a denial of service (crash).

Various Intrusion Detection Systems (IDS) including (1) Cisco Secure Intrusion Detection System, (2) Cisco Catalyst 6000 Intrusion Detection System Module, (3) Dragon Sensor 4.x, (4) Snort before 1.8.1, (5) ISS RealSecure Network Sensor 5.x and 6.x before XPU 3.2, and (6) ISS RealSecure Server Sensor 5.5 and 6.0 for Windows, allow remote attackers to evade detection of HTTP attacks via non-standard "%u" Unicode encoding of ASCII characters in the requested URL.

Snort 1.6, when running in straight ASCII packet logging mode or IDS mode with straight decoded ASCII packet logging selected, allows remote attackers to cause a denial of service (crash) by sending non-IP protocols that Snort does not know about, as demonstrated by an nmap protocol scan.