When accessing /cpanel, /webmail and /whm redirects I receive a 500 error. The following error is output via the Apache error_log:
AH01215: /usr/local/cpanel/3rdparty/bin/perl: error while loading shared libraries: libperl.so: failed to map segment from shared object: Cannot allocate memory: /usr/local/cpanel/cgi-sys/redirect.cgi
The issue is caused by Apache's Memory Usage Restrictions being set too low. This module can found in WHM's Apache Configuration module.
Either increase the memory limit being restricted or disable the restriction.