glibc LD_AUDIT Arbitrary DSO Load Privilege Escalation
Posted on 10 February 2018
This Metasploit module attempts to gain root privileges on Linux systems by abusing a vulnerability in the GNU C Library (glibc) dynamic linker. glibc ld.so in versions before 2.11.3, and 2.12.x before 2.12.2 does not properly restrict use of the LD_AUDIT environment variable when loading setuid executables. This allows loading arbitrary shared objects from the trusted library search path with the privileges of the suid user. This Metasploit module uses LD_AUDIT to load the libpcprofile.so shared object, distributed with some versions of glibc, and leverages arbitrary file creation functionality in the library constructor to write a root-owned world-writable file to a system trusted search path (usually /lib). The file is then overwritten with a shared object then loaded with LD_AUDIT resulting in arbitrary code execution. This Metasploit module has been tested successfully on glibc version 2.11.1 on Ubuntu 10.04 x86_64 and version 2.7 on Debian 5.0.4 i386. RHEL 5 is reportedly affected, but untested. Some glibc distributions do not contain the libpcprofile.so library required for successful exploitation.
