Docker Authorization Bypass Flaw Exposed Hosts to Potential Attackers

A critical security vulnerabilityhas been identified in Docker Engine, creating a risk of authorization bypass attacks against host systems.

Referred to as CVE-2026-34040, the flaw allows attackers to circumvent authorization plugins (AuthZ) by manipulating the content of an API request body.

While the inherent likelihood of exploitation remains low, this flaw carries a “High” severity classification.

The vulnerability specifically impacts environments where AuthZ plugins base access control decisions on the contents of an incoming request body.

Docker Authorization Bypass Flaw

The core vulnerability stems from how the Docker daemon handles excessively large request bodies. A malicious actor possessing low-level system access can send a specially crafted API request to the host.

This triggers a flaw where the Docker daemon forwards the request to the configured authorization plugin, but deliberately removes the request body content.

Because the AuthZ plugin lacks the necessary context provided by the request body, it is forced to make access decisions without complete information, potentially permitting actions it would normally block.

Effectively, the security mechanism making access control decisions operates blind to the request body, allowing malicious commands to pass through undetected.

Security researchers determined that this vulnerability originates from an incomplete fix for a prior Docker authorization flaw, tracked as CVE-2024-41110.

This specific vulnerability only applies to Docker Engine installations actively utilizing AuthZ plugins for security enforcement. Systems without AuthZ plugins in place for request inspection are not susceptible to this attack vector.

The flaw impacts all Docker Engine versions released prior to 29.3.1. Given the attack requires local system access and typically low privileges, it could potentially be exploited by a compromised container or a user with limited access to escalate privileges, alter host configurations, or access sensitive data.

Administrators are strongly advised to immediately upgrade to Docker Engine version 29.3.1, which includes the official security patch addressing this issue.

If immediate upgrade is not currently feasible, security teams should implement the following mitigation strategies:

• Discontinue use of AuthZ plugins that rely on examining the request body to make security decisions.
• Strictly limit Docker API access to trusted entities and adhere strictly to the principle of least privilege.

The vulnerability was responsibly disclosed by security researchers, with remediation efforts coordinated by the Docker development community.