The DecodeTCPOptions function in decode.c in Snort before 2.3.0, when printing TCP/IP options using FAST output or verbose mode, allows remote attackers to cause a denial of service (crash) via packets with invalid TCP/IP options, which trigger a null dereference.
https://exchange.xforce.ibmcloud.com/vulnerabilities/18689
https://euvd.enisa.europa.eu/vulnerability/EUVD-2004-2642
http://www.snort.org/arc_news/
http://www.securityfocus.com/bid/12084
http://www.securiteam.com/exploits/6X00L20C0S.html
http://www.frsirt.com/exploits/20041222.angelDust.c.php
http://taosecurity.blogspot.com/2004/12/details-on-snort-dos-condition-you-may.html