LearnCTEM.com, Best CTEM Learning Platform
CVE Intelligence Hub

CVE-2026-34040: Docker Engine Authentication Bypass via Alternate Path (CVSS 8.8)

CVE-2026-34040 is a high severity authentication bypass via alternate path in Docker Engine with a CVSS score of 8.8. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Last updated: Jun 17, 2026

Quick answer

Direct answer

CVE-2026-34040 is a high severity authentication bypass via alternate path in Docker Engine with a CVSS score of 8.8. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Risk scores

CVSS base score
8.8HIGH
EPSS probability
0.16%
Higher than 5 percent of all CVEs
CISA KEV
Not listed
CVSS metricWhat it means
Attack vector (AV:L)Local access needed
Attack complexity (AC:L)Low complexity
Privileges required (PR:L)Low privileges required
User interaction (UI:N)No user interaction
Scope (S:C)Scope changed: impact spreads beyond the component
Confidentiality (C:H)High confidentiality impact
Integrity (I:H)High integrity impact
Availability (A:H)High availability impact

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

About Docker Engine

CVE-2026-34040 affects Docker Engine, a product from Docker. Before acting, confirm where Docker Engine runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.

What the flaw is

In plain terms: Moby is an open source container framework. Prior to version 29.3.1, a security vulnerability has been detected that allows attackers to bypass authorization plugins (AuthZ). This issue has been patched in version 29.3.1.

The weakness class is Authentication Bypass via Alternate Path. A second route into the app skips the login check.

Based on its CVSS vector, the flaw needs local or adjacent access, needs some level of access, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Affected versions and timeline

FieldDetail
ProductDocker Engine
Affected versionsEngine before 29.3.1
PublishedMar 31, 2026
Last modifiedJun 17, 2026
Added to CISA KEVNot listed
Assigning CNAsecurity-advisories@github.com

How to detect it

  • Inventory every instance of Docker Engine and record the running version against the affected range above.
  • Check external attack surface scans for internet facing instances of the component.
  • Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
  • Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.

How to fix it

  • Apply the fixed version of Docker Engine named in the vendor advisory.
  • If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
  • Rescan after the change to prove the exposure is gone, then close the ticket.

CTEM action plan

CTEM stageWhat to do for this CVE
ScopeAdd every business service that depends on Docker Engine to the current CTEM cycle.
DiscoverFind all instances, including shadow and cloud deployments, and record versions and exposure.
PrioritizeRank using EPSS and CVSS together with asset exposure and business impact.
ValidateConfirm the flaw is reachable and exploitable in your environment and that compensating controls work.
MobilizeAssign the fix to the asset owner with a due date matched to the priority, then verify closure.

CWE References

Technical References

Frequently asked questions

CVE-2026-34040 is a high severity authentication bypass via alternate path in Docker Engine with a CVSS score of 8.8. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Related CVEs

HIGH7.2
CVE-2026-42306
Docker Engine

Moby is an open source container framework. In Docker Engine prior to version 29.5.1, Docker Daemon versions 28.5.2 and prior, and Moby Daemon prior to version 2.0.0-beta.14, a race condition during docker cp mount setup allows a malicious container to redirect a bind mount target to an arbitrary host path, potentially overwriting host files or causing denial of service. This issue has been patched in Docker Engine version 29.5.1 and Moby Daemon version 2.0.0-beta.14.

Jun 12, 2026
HIGH8.8
CVE-2026-5843
Docker Desktop

The MLX inference backend in Docker Model Runner on macOS uses the MLX-LM library, which unconditionally imports and executes arbitrary Python files from model directories via the model_file configuration field in config.json. When a model's config.json specifies a model_file pointing to a Python file, MLX-LM uses importlib to load and execute it with no trust_remote_code gate or equivalent safety check. The MLX backend runs without sandboxing, resulting in arbitrary code execution on the Docker host as the Docker Desktop user. Any container on the Docker network can trigger this by calling the model-runner.docker.internal API to pull a malicious model from an attacker-controlled OCI registry and request inference.

May 22, 2026
HIGH8.8
CVE-2026-5817
Docker Desktop

The vllm-metal inference backend in Docker Model Runner on macOS unconditionally sets trust_remote_code=True when loading model tokenizers, and runs without sandboxing. This causes transformers.AutoTokenizer.from_pretrained() to import and execute arbitrary Python files included in any model pulled from an OCI registry, resulting in arbitrary code execution on the Docker host as the Docker Desktop user when inference is triggered. Any container on the Docker network can trigger this by calling the model-runner.docker.internal API to pull a malicious model and request inference.

May 22, 2026
HIGH7.0
CVE-2025-15558
Docker Command Line Interface

Docker CLI for Windows searches for plugin binaries in C:\ProgramData\Docker\cli-plugins, a directory that does not exist by default. A low-privileged attacker can create this directory and place malicious CLI plugin binaries (docker-compose.exe, docker-buildx.exe, etc.) that are executed when a victim user opens Docker Desktop or invokes Docker CLI plugin features, and allow privilege-escalation if the docker CLI is executed as a privileged user. This issue affects Docker CLI: through 29.1.5 and Windows binaries acting as a CLI-plugin manager using the github.com/docker/cli/cli-plugins/manager https://pkg.go.dev/github.com/docker/cli@v29.1.5+incompatible/cli-plugins/manager  package, such as Docker Compose. This issue does not impact non-Windows binaries, and projects not using the plugin-manager code.

Mar 4, 2026
CRITICAL10.0
CVE-2025-64121
Nuvationenergy Nplatform

Authentication Bypass Using an Alternate Path or Channel vulnerability in Nuvation Energy Multi-Stack Controller (MSC) allows Authentication Bypass.This issue affects Multi-Stack Controller (MSC): from 2.3.8 before 2.5.1.

Jan 2, 2026
CRITICAL9.9
CVE-2026-10523
Ivanti Standalone Sentry

An Authentication Bypass vulnerability (CWE-288) in Ivanti Sentry before the R10.5.2, R10.6.2 and R10.7.1 versions allows a remote unauthenticated attacker to create arbitrary administrative accounts and obtain full administrative access

Jun 9, 2026
All Docker CVEs in 2026
Your next credential

Earn your free CTEM certification.

Learn to scope, prioritize, validate and mobilize fixes for CVEs like CVE-2026-34040 with a free CTEM certification.

Free to takePublicly verifiable

Beginner / Practitioner / Program Leader

Explore certifications