The log files in Apache web server contain information directly supplied by clients and does not filter or quote control characters, which could allow remote attackers to hide HTTP requests and spoof source IP addresses when logs are viewed with UNIX programs such as cat, tail, and grep.

Cross site scripting vulnerabilities in Apache 1.3.0 through 1.3.11 allow remote attackers to execute script as other web site visitors via (1) the printenv CGI (printenv.pl), which does not encode its output, (2) pages generated by the ap_send_error_response function such as a default 404, which does not add an explicit charset, or (3) various messages that are generated by certain Apache modules or core code. NOTE: the printenv issue might still exist for web browsers that can render text/plain content types as HTML, such as Internet Explorer, but CVE regards this as a design limitation of those browsers, not Apache. The printenv.pl/acuparam vector, discloser on 20070724, is one such variant.