It was discovered that the HTTP parser in httpd incorrectly allowed certain characters not permitted by the HTTP protocol specification to appear unencoded in HTTP request headers. If httpd was used in conjunction with a proxy or backend server that interpreted those characters differently, a remote attacker could possibly use this flaw to inject data into HTTP responses, resulting in proxy cache poisoning.
Unitrends risk assessment: Medium, or None if current security update is applied
For CentOS6, Unitrends security update dated 11/06/2017 or later has httpd-2.2.15-60.el6.centos.6 and this issue was fixed in httpd-2.2.15-60.el6.centos.4 / httpd-2.2.15-60.el6_9.4
For CentOS5, the system should be migrated to CentOS6.
LINK TO ADVISORIES