Integer underflow in the DecodeGRE function in src/decode.c in Snort 2.6.1.2 allows remote attackers to trigger dereferencing of certain memory locations via crafted GRE packets, which may cause corruption of log files or writing of sensitive information into log files.
http://www.vupen.com/english/advisories/2007/0152
http://www.snort.org/got_source/source.html
http://www.securityfocus.com/bid/22004
http://www.securityfocus.com/archive/1/456598/100/0/threaded
http://securitytracker.com/id?1017507