External risk intelligence

Kyverno Namespace Escape via Resource Argument Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.4)

CVE-2026-122311

Kyverno is a Kubernetes admission controller that operates within the cluster control plane. While it interacts with cluster resources, it is designed for internal infrastructure management, not for direct public internet exposure. Access to create NamespacedValidatingPolicies is generally restricted to authenticated internal users or automated systems within the cluster environment, making direct public-facing exploitation unlikely.

Path Traversal

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

A security vulnerability has been identified in Kyverno affecting how it validates resource paths, potentially allowing some policies to access information outside their designated namespaces. This could enable unauthorized users with specific permissions to interact with sensitive cluster resources. The primary concern is to determine if your environment utilizes the affected Kyverno versions and configurations.

Policies can escape their intended scope.
Allows access to sensitive cluster resources.
Confirm relevance and exposure in your environment.

Attack Path

How an attacker could exploit the issue

An attacker with the ability to create NamespacedValidatingPolicy in Kyverno could leverage a flaw in how resource arguments are validated. By manipulating path segments within the resource argument, the attacker can bypass namespace restrictions and access arbitrary cluster objects. This allows them to read and write cluster resources, ultimately leading to a complete takeover of the Kubernetes cluster.

Requires authenticated access to create policies.
Uses path traversal to escape namespace.
Enables arbitrary cluster object manipulation.

Live Threat

Current exploitation, exposure, and threat context

Kyverno policies, when configured to allow namespace escape, could enable unauthorized access to and modification of arbitrary cluster objects. This could occur when a tenant with the ability to create specific types of policies inserts directory traversal sequences into resource arguments, allowing them to interact with resources outside their designated namespace using the admission controller's service account.

Arbitrary cluster objects.
Malicious policy input.
Cluster takeover.

Operational Fix

Recommended remediation, mitigation, and detection steps

The Kyverno admission controller's vulnerability requires immediate attention from Kubernetes platform teams and security operations. The first practical step is to identify all Kyverno deployments, assess their exposure to unauthenticated or low-privileged access that could trigger the vulnerability, and determine their criticality to cluster operations. This will enable proper risk-based prioritization and coordinated remediation planning with application owners.

Platform and Security teams own.
Verify resource.get()/post() reachability.
Plan remediation with application owners.

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 Kyverno?

Kyverno is an admission controller for Kubernetes, designed to manage, validate, and mutate resource configurations automatically. It runs within the cluster control plane, enforcing policies that ensure applications adhere to operational standards and security requirements, acting as a safeguard for infrastructure integrity.

What does CVE-2026-122311 mean?

This vulnerability is a path traversal flaw (CWE-22) affecting Kyverno's CEL policy engine. Because the software fails to sanitize path segments in resource.get() and resource.post() calls, a user who can define a policy can trick the system into looking for resources outside of its intended namespace, effectively breaking the logical isolation boundaries of the cluster.

How can an attacker trigger this vulnerability?

An attacker needs the privilege to create a NamespacedValidatingPolicy within the cluster. By inserting path traversal sequences (like '..') into the resource argument of a policy, they force the admission controller to access objects it should not reach. Simple or legitimate policy configurations that do not utilize these specific path-based resource functions are not affected.

Is my cluster at risk?

Risk depends on who has permission to create NamespacedValidatingPolicies. According to Halo Surface Signal, Kyverno typically resides within internal infrastructure, making direct public exploitation unlikely. However, if internal users or automated systems have broad permissions to define these policies, the risk increases significantly, as an attacker could gain control over the cluster via the admission controller's service account.

What should I do to address this?

First, inventory all Kyverno instances to confirm if you are running versions between 1.16.0 and 1.19.2. Identify which users or automated processes have the authority to create NamespacedValidatingPolicies and review existing policies for suspicious resource arguments. Coordinate with your platform teams to prioritize updates and restrict policy creation permissions to trusted users only.

References

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.