Check: WA000-WWA032 A24
Apache Server 2.4 Unix:
WA000-WWA032 A24
(in version v1 r1)
Title
The httpd.conf MaxRequestWorkers directive must be set properly. (Cat II impact)
Discussion
These requirements are set to mitigate the effects of several types of denial of service attacks. Although there is some latitude concerning the settings themselves, the requirements attempt to provide reasonable limits for the protection of the web server. If necessary, these limits can be adjusted to accommodate the operational requirement of a given system. From Apache.org: The MaxRequestWorkers directive sets the limit on the number of simultaneous requests that will be served. Any connection attempts over the MaxRequestWorkers limit will normally be queued, up to a number based on the ListenBacklog directive. Once a child process is freed at the end of a different request, the connection will then be serviced. For non-threaded servers (i.e., prefork), MaxRequestWorkers translates into the maximum number of child processes that will be launched to serve requests. The default value is 256; to increase it, you must also raise ServerLimit. For threaded and hybrid servers (e.g. event or worker) MaxRequestWorkers restricts the total number of threads that will be available to serve clients. For hybrid MPMs the default value is 16 (ServerLimit) multiplied by the value of 25 (ThreadsPerChild). Therefore, to increase MaxRequestWorkers to a value that requires more than 16 processes, you must also raise ServerLimit.
Check Content
To view the MaxRequestWorkers value enter the following command: find / -name httpd.conf -print -exec grep -H -i "MaxRequestWorkers" {} \; If the value of "MaxRequestWorkers" is not 256 or less, this is a finding. If the directive does not exist, this is NOT a finding because it will default to 256. It is recommended that the directive be explicitly set to prevent unexpected results if the defaults change with updated software. NOTE: This vulnerability can be documented locally with the ISSM/ISSO if the site has operational reasons for the use of increased value. If the site has this documentation, this should be marked as Not a Finding.
Fix Text
Edit the httpd.conf file and set the value of "MaxRequestWorkers" to a value of 256 or less, add the directive if it does not exist.
Additional Identifiers
Rule ID:
Vulnerability ID: V-13730
Group Title:
Expert Comments
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