Warning and error messages displayed to clients must be modified to minimize the identity of the web server, patches, loaded modules, and directory paths.

From Web Server Security Requirements Guide

Associated with: CCI-001312

SV-54431r3_rule Warning and error messages displayed to clients must be modified to minimize the identity of the web server, patches, loaded modules, and directory paths.

Vulnerability discussion

Information needed by an attacker to begin looking for possible vulnerabilities in a web server includes any information about the web server, backend systems being accessed, and plug-ins or modules being used. Web servers will often display error messages to client users displaying enough information to aid in the debugging of the error. The information given back in error messages may display the web server type, version, patches installed, plug-ins and modules installed, type of code being used by the hosted application, and any backends being used for data storage. This information could be used by an attacker to blueprint what type of attacks might be successful. The information given to users must be minimized to not aid in the blueprinting of the web server.

Check content

Review the web server documentation and deployed configuration to determine whether the web server offers different modes of operation that will minimize the identity of the web server, patches, loaded modules, and directory paths given to clients on error conditions. If the web server is not configured to minimize the information given to clients, this is a finding.

Fix text

Configure the web server to minimize the information provided to the client in warning and error messages.

Pro Tips

Lavender hyperlinks in small type off to the right (of CSS class id, if you view the page source) point to globally unique URIs for each document and item. Copy the link location and paste anywhere you need to talk unambiguously about these things.

You can obtain data about documents and items in other formats. Simply provide an HTTP header Accept: text/turtle or Accept: application/rdf+xml.