Northern Solutions Xeneo Web Server 2.1.0.0, 2.0.759.6, and other versions before 2.1.5 allows remote attackers to cause a denial of service (crash) via a GET request for a "%" URI.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2002-1232
http://www.securityfocus.com/bid/6098
http://www.iss.net/security_center/static/10534.php