External risk intelligence

Consul-k8s Cross-Namespace Authorization Bypass Allows Privilege Escalation

CVE advisorySeverity: CRITICAL (CVSS 9.9)

CVE-2026-110720

Consul-k8s is a component used to integrate HashiCorp Consul with Kubernetes clusters. It operates within the orchestration layer for internal service discovery and configuration management. While it interacts with network-based APIs, it is typically deployed deep within internal infrastructure and is not designed to be directly exposed to the public internet.

Halo Surface Signal: 2 out of 5 — less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This vulnerability affects the integration of Consul with Kubernetes, potentially allowing unauthorized access and elevated privileges within the Consul environment. The primary concern is to confirm if this technology is used within our environment and assess any potential exposure.

Authorization bypass in Consul-k8s integration.
Attackers gain elevated Consul privileges.
Confirm relevance and exposure to our systems.

Attack Path

How an attacker could exploit the issue

An attacker with limited privileges could exploit this vulnerability by targeting the ACL binding rules within Consul-k8s. By manipulating these rules, they could bypass authorization checks and gain elevated Consul privileges, potentially leading to unauthorized access and control over Consul resources.

Requires limited privileges.
Exploits ACL binding rules.
Results in elevated Consul privileges.

Live Threat

Current exploitation, exposure, and threat context

Consul-k8s versions 0.42.0 and later contain a vulnerability in ACL binding rules that could allow an attacker to bypass cross-namespace authorization. When supported by the advisory, this could enable an attacker to gain elevated privileges within Consul.

Elevated Consul privileges.
Bypass cross-namespace authorization rules.
Gain unauthorized access to Consul resources.

Operational Fix

Recommended remediation, mitigation, and detection steps

This critical vulnerability affects Consul-k8s, a component integrating Consul with Kubernetes. Platform or infrastructure teams managing Kubernetes and Consul deployments are likely responsible for remediation. The immediate first step is to identify all instances of Consul-k8s, determine their reachability and criticality, and identify the accountable owner before planning risk-based remediation.

Identify Consul-k8s instances and owners.
Verify reachability and business criticality.
Plan risk-based remediation and vendor coordination.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is consul-k8s and why is it used?

Consul-k8s is a software component that bridges HashiCorp Consul with Kubernetes. It enables Consul to operate within Kubernetes clusters, providing service discovery and configuration management for containerized applications. It acts as the orchestration layer that allows services across the cluster to locate and communicate with each other securely.

What does CVE-2026-110720 mean in simple terms?

This vulnerability is an authorization bypass, classified as CWE-863. It means the system fails to correctly verify user permissions when handling Access Control List (ACL) binding rules across different namespaces. Essentially, it creates a loophole where an attacker can act as if they have higher-level administrative rights than they were granted, potentially gaining full control over Consul resources.

How does an attacker trigger this vulnerability?

An attacker needs existing limited privileges within the environment to manipulate the ACL binding rules. They must be able to interact with the Consul-k8s component's configuration logic. This bug is not triggered by public, unauthenticated network traffic; it specifically requires the ability to influence the cross-namespace authorization checks used to assign privileges.

Is this CVE likely to be reachable from the internet?

According to Halo Surface Signal, this is unlikely. Because consul-k8s functions as an internal service discovery and orchestration tool, it is typically deployed deep within an organization's private infrastructure. It is not intended to be exposed to the public internet, which generally limits the ability of external actors to reach the vulnerable component.

What should I do if I use consul-k8s?

Your first step is to inventory all deployments of consul-k8s to identify which instances are currently running version 0.42.0 or later. Once you have identified these systems and their accountable owners, coordinate with your infrastructure team to plan an upgrade to version 2.1.0 or 1.8.18, which contain the necessary security fixes for this flaw.

References

discuss.hashicorp.com/t/hcsec-2026-50-consul-k8s-vulnerable-to-a-cross-name…

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.