The CHECK command in Cosign 2.0.1 and earlier allows remote attackers to bypass authentication requirements via CR (\r) sequences in the cosign cookie parameter.
http://www.vupen.com/english/advisories/2007/1359
http://www.umich.edu/~umweb/software/cosign/cosign-vuln-2007-001.txt
http://www.securityfocus.com/archive/1/465386/100/100/threaded