Docker Authorization Bypass Flaw Exposed Hosts to Potential Attackers

A high-severity security vulnerability has been discovered in Docker Engine, exposing hosts to potential authorization bypass attacks.

Tracked as CVE-2026-34040, the flaw allows attackers to evade authorization plugins (AuthZ) by manipulating API request bodies.

While the base likelihood of exploitation remains low, the vulnerability carries a “High” severity rating.

It specifically impacts environments relying on AuthZ plugins to make access control decisions based on the contents of an incoming request body.

Docker Authorization Bypass Flaw

The core of the issue lies in how the Docker daemon processes oversized request bodies. An attacker with low-level access can send a specially crafted API request to the system.

This triggers a flaw where the Docker daemon forwards the request to the active authorization plugin, but strips away the request body.

Because the AuthZ plugin lacks the necessary data to properly evaluate the request, it may allow an action that it would normally block.

Essentially, the security gatekeeper is forced to make a blind decision, allowing malicious commands to slip through unnoticed.

Security researchers noted that this vulnerability stems from an incomplete fix for a previous Docker authorization flaw, tracked as CVE-2024-41110.

This vulnerability only affects users who actively utilize AuthZ plugins. If your Docker environment does not rely on these plugins for security checks, your systems are not vulnerable to this specific attack.

The flaw impacts all Docker Engine versions prior to 29.3.1. Because the attack requires local access and low privileges, a compromised container or limited user account could potentially exploit this to escalate privileges, alter host configurations, or access sensitive data.

To secure affected systems, administrators should immediately upgrade to Docker Engine version 29.3.1, which contains the official patch.

If immediate updating is not feasible, security teams can implement the following workarounds:

• Stop using AuthZ plugins that rely on request body inspection for security decisions.
• Restrict access to the Docker API strictly to trusted parties, enforcing the principle of least privilege.

The vulnerability was responsibly disclosed by a team of security researchers, with remediation efforts led by the Docker development community.

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