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CVE-2026-34040 is a high-severity authorization bypass vulnerability in Docker Engine and Moby affecting versions prior to 29.3.1. The flaw exists in the middleware path between the Docker API and authorization plugins (AuthZ) that make policy decisions by inspecting API request bodies. When an attacker submits a specially crafted Docker API request with an oversized body, reported as larger than 1 MB in the vulnerable implementation, the middleware can forward the request to the AuthZ plugin without the body while the Docker daemon still processes the complete original request body. This discrepancy allows the authorization plugin to evaluate an incomplete request and potentially approve an operation it would have denied if the full body had been available. The issue has been described as an incomplete fix for CVE-2024-41110. Successful exploitation can permit unauthorized Docker operations such as creating containers with restricted or excessive privileges.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository is a Python-based full lab PoC for CVE-2026-34040, targeting Docker/Moby AuthZ plugin bypass behavior when a Docker API request body exceeds 1 MB. The repository is small and focused: one executable script (poc.py), a standard-library-only requirements file, and several Markdown documents covering setup, demo flow, impact modes, troubleshooting, and publication notes. The main exploit logic is in poc.py. It manually crafts raw HTTP requests over the local UNIX socket /var/run/docker.sock rather than using the Docker SDK. The key capability is sending a container creation request with oversized JSON label padding ("padding" = "A" * (1024*1024+1)) so that an AuthZ plugin may fail to inspect the body while the Docker daemon still processes the original request. The script compares a normal request against an oversized one in check mode to determine whether the bypass is observable, expecting small requests to be blocked (HTTP 403) and oversized requests to reach daemon processing (HTTP 201 or possibly HTTP 404 if the image is missing). Beyond detection, the PoC includes multiple post-bypass impact modes. These include reading host files by creating a privileged container with the host root mounted read-only, writing a proof marker file on the host via chroot, executing user-supplied host commands in a lab, creating a long-lived privileged container for manual docker exec and chroot interaction, and a local-only reverse shell mode restricted to 127.0.0.1/localhost. The README and docs explicitly describe that the vulnerability itself is an authorization bypass, while file read and command execution are downstream impacts enabled by privileged container creation plus host bind mounts. Repository structure: README.md explains the vulnerability model, usage, and safety notes; docs/lab-setup.md lists prerequisites such as vulnerable Docker/Moby, AuthZ plugin, docker.sock access, and local alpine image; docs/impact-modes.md and docs/demo-script.md describe each demonstration path; docs/troubleshooting.md covers common failures like missing image or socket permissions. Overall, this is a real exploit PoC for local lab use, not merely a detector, and it is operational because it contains working payload paths for host file access and host command execution.
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59 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A historical Moby vulnerability mentioned for background context.
A Docker vulnerability involving an authorization plugin bypass caused by a documentation-code mismatch.
An authorization bypass vulnerability affecting Docker/Moby.
A high-severity authorization bypass vulnerability in Docker Engine AuthZ handling that allows specially crafted API requests with bodies larger than 1MB to evade AuthZ inspection and reach the Docker daemon, enabling actions such as creating privileged containers.
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