Symlink Protection for cPanel is much important . Symlink attack occurs after the attacker has been able to read the contents of the /etc/passwd file and has enumerated the server’s users.
Symlink race condition vulnerability
If you enable both of the
FollowSymLinks configuration settings, Apache becomes vulnerable to a race condition through symlinks. This symlink vulnerability allows a malicious user to serve files from anywhere on a server that strict OS-level permissions do not protect.
Filesystem-level solutions : Enable mod_ruid + jailshell for your apache webserver.
To enable this option, recompile Apache and then enable EXPERIMENTAL: Jailshell Virtual Hosts using mod_ruid2 and cPanel jailshell in WHM’s Tweak Settings interface (Home >> Server Configuration >> Tweak Settings).
CageFS is a virtualized file system and a set of tools to contain each user in its own ‘cage’. This option is available on all cPanel-supported platforms today, and it is already included with CloudLinux.
CloudLinux SecureLinks is a safe option to address the race condition vulnerability. This option prevents symlink attacks at the kernel level. CloudLinux installs this option by default, but it does not affect virtual hosts that do not specify a user ID.
For more information, read the CloudLinux documentation.
GRSec kernel patch
The GRSec kernel patch is a safe option to address the race condition vulnerability. This patch provides kernel-level protection against race conditions. However, to use it, you must use a custom kernel, which requires additional installation and maintenance.
For more information, read the Prevent Symlink Attack information on the grsecurity forums.