Directory traversal vulnerability in ssi CGI program in thttpd 2.19 and earlier allows remote attackers to read arbitrary files via a "%2e%2e" string, a variation of the .. (dot dot) attack.
https://exchange.xforce.ibmcloud.com/vulnerabilities/5313
https://euvd.enisa.europa.eu/vulnerability/EUVD-2000-0887
http://www.securityfocus.com/bid/1737
http://archives.neohapsis.com/archives/bugtraq/2000-10/0025.html