Apache 1.3 through 1.3.24, and Apache 2.0 through 2.0.36, allows remote attackers to cause a denial of service and possibly execute arbitrary code via a chunk-encoded HTTP request that causes Apache to use an incorrect size.

PHP, when installed with Apache and configured to search for index.php as a default web page, allows remote attackers to obtain the full pathname of the server via the HTTP OPTIONS method, which reveals the pathname in the resulting error message.

PHP for Windows, when installed on Apache 2.0.28 beta as a standalone CGI module, allows remote attackers to obtain the physical path of the php.exe via a request with malformed arguments such as /123, which leaks the pathname in the error message.

The ap_log_rerror function in Apache 2.0 through 2.035, when a CGI application encounters an error, sends error messages to the client that include the full path for the server, which allows remote attackers to obtain sensitive information.

Apache for Win32 before 1.3.24, and 2.0.x before 2.0.34-beta, allows remote attackers to execute arbitrary commands via shell metacharacters (a | pipe character) provided as arguments to batch (.bat) or .cmd scripts, which are sent unfiltered to the shell interpreter, typically cmd.exe.

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.