CVE-2026-34040 — Docker/Moby AuthZ Plugin Bypass (Lab PoC)

EN: A lab reproduction of a vulnerability that bypasses Docker (Moby) authorization (AuthZ) plugins using an oversized (>1MB) request body.

Vulnerability facts

EN: The official CVSS vector is AV:L (Local). The rated scenario is a low-privileged user with local Docker API access (typically /var/run/docker.sock). This PoC uses the local UNIX socket only.

What this demonstrates

EN:

1. A normal-sized privileged container-create request is blocked by the AuthZ plugin (HTTP 403).
2. The same request padded beyond 1MB bypasses the AuthZ check.
3. The bypassed request reaches the Docker daemon and creates a privileged container.
4. With privileged + host bind mount, host file read and host command execution can be demonstrated.

EN: The CVE itself does not read /etc/shadow or perform RCE directly. The vulnerability is the bypass of a Docker API request that AuthZ should block; the later steps (file read, chroot, command execution) are impact demos that abuse normal Docker/Linux features.

Repository structure

.
├── README.md
├── poc.py                  # Working PoC (local UNIX socket only)
├── requirements.txt        # Python standard library only
├── LICENSE
├── lab/
│   ├── authz.rego          # OPA policy: blocks privileged + host-root bind
│   └── daemon.json         # Registers the AuthZ plugin
└── docs/
    ├── concepts.md         # 개념 / Concepts
    ├── lab-setup.md        # 환경 구성 / Lab setup
    ├── how-it-works.md     # 동작 원리 / How it works (source-level)
    ├── usage.md            # 사용법 / Usage
    ├── troubleshooting.md  # 문제 해결 / Troubleshooting
    └── references.md       # 참고 / References

Prerequisites

Quick start

# 1) Pull the image used by the PoC
sudo docker pull alpine

# 2) Run the non-destructive bypass check
sudo python3 poc.py --mode check

Expected on a vulnerable target:

small request     -> HTTP 403   (AuthZ blocks)
oversized request -> HTTP 201 or HTTP 404   (AuthZ bypassed; daemon processed it)

EN: A 404 No such image is still evidence of bypass — the request passed AuthZ (not 403) and reached the daemon's image lookup. Pull alpine beforehand to avoid confusion in a demo.

See docs/usage.md for full usage.

Lab-only warning

EN: Use only in an isolated lab you own or are explicitly authorized to test. Do not run against remote Docker APIs, third-party servers, production, or internet-exposed Docker endpoints. The impact-demo modes (rce-proof, host-command, reverse-shell-local) require an explicit confirmation flag.

References

See docs/references.md.