This Metasploit module attempts to gain root privileges on Linux systems by abusing a vulnerability in GNU C Library (glibc) version 2.26 and prior. This Metasploit module uses halfdog’s RationalLove exploit to exploit a buffer underflow in glibc realpath() and create a SUID root shell. The exploit has offsets for glibc versions 2.23-0ubuntu9 and 2.24-11+deb9u1. The target system must have unprivileged user namespaces enabled. This Metasploit module has been tested successfully on Ubuntu Linux 16.04.3 (x86_64) with glibc version 2.23-0ubuntu9; and Debian 9.0 (x86_64) with glibc version 2.24-11+deb9u1.

Source: glibc ‘realpath()’ Privilege Escalation