Title

The UrlSegmentMaxCount registry entry must be set properly. (Cat II impact)

Discussion

Http.sys is the kernel mode driver that handles HTTP requests. There are several registry keys associated with http.sys. The UrlSegmentMaxCount value determines the maximum number of URL path segments accepted by the server. It effectively limits the number of slashes that can be included by the user in a request URL. It is recommended to set fairly stringent limits on this value based on the depth of the web document root tree to protect the server from a file system traversal attack.

Check Content

1. Open the registry editor. 2. Navigate to the following location in the registry: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\HTTP\Parameters. 3. Set the value for the UrlSegmentMaxCount key is set to REG_DWORD 255 (or less). If the registry value is not set to 255 (or less) or is missing, this is a finding.

Fix Text

1. Open the registry editor. 2. Navigate to the following location in the registry: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\HTTP\Parameters. 3. Set the value for the UrlSegmentMaxCount key to REG_DWORD 255 (or less) or add the key and set it to REG_DWORD 255.

Additional Identifiers

Rule ID: SV-38168r1_rule

Vulnerability ID: V-13722

Group Title:

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.