External risk intelligence

Kyverno Authorization Bypass Allows Cross-Namespace Resource Overwrite.

CVE advisorySeverity: CRITICAL (CVSS 9.4)

CVE-2026-122303

Kyverno is a Kubernetes-native policy engine that operates as an internal cluster controller. It is not designed to be directly exposed to the public internet. While it processes network-based requests within the cluster environment, it is typically protected by internal Kubernetes network policies and authentication controls, making public internet exposure uncommon in standard deployments.

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 advisory details a critical vulnerability in Kyverno, a policy engine for Kubernetes, that could allow unauthorized users to overwrite critical cluster resources across different namespaces. The issue stems from an authorization bypass within the NamespacedMutatingPolicy, enabling malicious actors to manipulate sensitive data like Secrets and Deployments. The primary concern is to verify if our environment uses this technology and is exposed to this risk.

Unauthorized users can overwrite cluster resources.
This impacts the integrity of Kubernetes cluster data.
Confirm relevance and assess potential exposure.

Attack Path

How an attacker could exploit the issue

An attacker with tenant-level access within a Kubernetes cluster could exploit this vulnerability by crafting a malicious policy. This policy, when processed by the Kyverno component, could be manipulated to target and overwrite critical resources like Secrets or Deployments in namespaces beyond the attacker's own. This unauthorized access and modification can disrupt cluster operations and compromise sensitive data.

Requires authenticated tenant access.
Attacker crafts a policy targeting specific resources.
Risk of cluster-wide resource overwrites.

Live Threat

Current exploitation, exposure, and threat context

When supported by the advisory, this vulnerability could allow namespace tenants to overwrite resources in other namespaces and potentially affect cluster-wide Secrets, Deployments, or policies.

Cluster-wide Secrets, Deployments, or policies at risk.
Namespace tenants could overwrite resources.
Unrestricted resource modification in the cluster.

Operational Fix

Recommended remediation, mitigation, and detection steps

Platform and security teams are likely responsible for addressing this authorization bypass vulnerability in Kyverno, as it allows namespace tenants to overwrite resources cluster-wide. The initial step involves identifying all Kyverno instances, confirming their reachability and criticality, and then locating the accountable owners to plan remediation based on the assessed risk.

Platform and security teams own this.
Verify Kyverno instance reachability and criticality.
Plan coordinated remediation based on risk.

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 and how is it used?

Kyverno is a policy engine designed specifically for Kubernetes. It functions as an admission controller that validates, mutates, and generates configurations for your cluster. Organizations use it to enforce security standards, ensure compliance, and automate routine configuration tasks by defining policies as native Kubernetes resources.

What does CWE-862 mean for CVE-2026-122303?

CWE-862 represents an improper authorization weakness. In the context of CVE-2026-122303, this means the software fails to properly check if a user is permitted to perform a specific action. Specifically, Kyverno allows users with limited, single-namespace permissions to bypass these boundaries and manipulate resources in namespaces they do not own.

How does an attacker trigger this vulnerability?

An attacker needs existing authenticated tenant access within the cluster to trigger this issue. They exploit it by submitting a specially crafted NamespacedMutatingPolicy that uses a CEL map literal to deceive the controller. This bug does not trigger if the attacker lacks the permissions to create or modify Kyverno policies within their own namespace.

Is my cluster at risk if Kyverno is internal?

According to Halo Surface Signal, Kyverno is an internal cluster controller and is not typically exposed to the public internet. However, because the vulnerability relies on abusing existing tenant access, the risk remains relevant if untrusted users have permission to create policies within your cluster, regardless of whether the management interface is public.

What are the first steps to address this CVE?

Start by identifying all Kyverno instances deployed across your environments and verifying their current versions. If you are running a version between 1.17.0 and 1.19.2, coordinate with your platform and security teams to prioritize an update to a patched version. Assessing which users currently have policy-creation permissions can also help limit the attack surface while you plan your remediation.

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.