Showing posts from November, 2023

Exploit & Debug Looney Tunables CVE-2023-4911 Local Privilege Escalation in the glibc's

Hoi, let's try to debug and explain CVE-2023-4911 which is a buffer overflow in the glibc loader my debugging and exploit tested on Ubuntu 22.04.2 (Jammy Jellyfish), you can read the analysis and more information from the Qualys Security writeup . POC to check if you are vulnerable or not env -i "GLIBC_TUNABLES=glibc.malloc.mxfast=glibc.malloc.mxfast=A" "Z=`printf '%08192x' 1`" /usr/bin/su --help My exploit POC video takes 5m but I speeded up the video Preparing let's disable ASLR and debug our exploit echo 0 | sudo tee /proc/sys/kernel/randomize_va_space you have to know (from qualys security): On Linux, the stack is randomized in a 16GB region, and our environment strings can occupy up to 6MB (_STK_LIM / 4 * 3, in the kernel's bprm_stack_limits()): after 16GB / 6MB = 2730 tries we have a good chance of guessing the address of our environment strings. using the buffer overflow vulnerability in the tunables we will overflow the link_map struct wh