CVE-2026-54523 is a critical-severity (CVSS 9.6) CWE-862 vulnerability in github.com/kyverno/kyverno. O3 Security confirms whether CVE-2026-54523 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Kyverno's NamespacedGeneratingPolicy generator.apply() namespace argument unvalidated -- background controller creates RoleBindings in any namespace including kube-system
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-54523.
Real-World Exposure
github.com/kyverno/kyvernoReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Summary
In Kyverno v1.18.1, a tenant who can create a NamespacedMutatingPolicy in their own namespace can instruct the admission controller to generate resources in any namespace by passing an arbitrary namespace string to the CEL generator.apply(namespace, resources) function.
Details
pkg/cel/libs/context.go:177 declares GenerateResources(namespace string, dataList []map[string]any). The namespace argument arrives unvalidated from the CEL expression generator.apply("<target-namespace>", [...]).
Version-Specific Impact
v1.18.0, v1.18.1 (affected via NamespacedMutatingPolicy only):
The nmpol CEL compiler unintentionally exposes the generator library to match condition expressions. A namespaced mutating policy can invoke generator.apply() in a boolean CEL expression such as matchConditions, triggering the admission controller to generate resources in any namespace at request time. This side effect executes with the admission controller's cluster-wide privileges.
NamespacedGeneratingPolicy is not a vector in v1.18.1 due to incomplete webhook and background processing wiring (not registered or functional).
Root Cause
The admission validator for NamespacedMutatingPolicy (pkg/cel/policies/mpol/validate.go) only checks that the policy compiles and does not enforce namespace scope on generator.apply() arguments.
Compare correctly-guarded equivalents: pkg/engine/context/loaders/configmap.go:102 rejects cross-namespace ConfigMap references for namespaced policies, and pkg/engine/apicall/apicall.go:73-82 enforces namespace segment matching. GenerateResources has neither guard.
Proof of Concept
Prerequisites: namespace tenant-ns exists; attacker has create on namespacedmutatingpolicies.policies.kyverno.io in tenant-ns.
apiVersion: policies.kyverno.io/v1beta1
kind: NamespacedMutatingPolicy
metadata:
name: cross-ns-escalate
namespace: tenant-ns
spec:
matchConstraints:
resourceRules:
- apiGroups: [""]
apiVersions: ["v1"]
resources: ["configmaps"]
operations: ["CREATE"]
mutations:
- patchType: applyConfiguration
applyConfiguration:
expression: object
matchConditions:
- name: trigger-escalation
expression: |
generator.apply("kube-system", [
{
"apiVersion": dyn("v1"),
"kind": dyn("ConfigMap"),
"metadata": dyn({
"name": "kube-system-config",
"namespace": "kube-system"
}),
"data": dyn({
"injected-by": "tenant-policy",
"impact": "unauthorized access to kube-system namespace"
})
}
])
Apply the policy, then create any ConfigMap in tenant-ns to trigger the admission webhook. The admission controller creates configmap/kube-system-config in kube-system. By default, the admission controller has create on ConfigMaps in all namespaces.
Impact
A namespace-scoped user with create on NamespacedMutatingPolicy in >=v1.18.1 can create ConfigMaps, NetworkPolicies, Secrets, and other resources in any namespace using the admission controller's cluster-wide RBAC. This allows:
Injecting sensitive configuration into protected namespaces (e.g., kube-system, default)
Disrupting cluster networking via NetworkPolicies
Privilege escalation via RoleBinding creation (for roles the admission controller holds or lesser-privileged roles)
Privilege escalation via RoleBinding creation in other namespaces
Any installation that grants non-admin users access to NamespacedMutatingPolicy creation is affected.
Timeline
- 2026-05-20: Vulnerability reproduced on main
- 2026-07-13: CVE-2026-54523 / GHSA-79gf-7frw-68m9 published
- 2026-07-22: Advisory clarified to document actual v1.18.1 attack vector (NamespacedMutatingPolicy in matchConditions, not NamespacedGeneratingPolicy)
Advisory Update
This advisory was updated to clarify the v1.18.1 attack surface. The nmpol vector in matchConditions was the reachable attack path in v1.18.1, while ngpol lacked end-to-end plumbing. The CVE, patched version, and CVSS score remain unchanged. Original report by @0xVijay.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/kyverno/kyverno | ≥ 1.18.0&&< 1.18.2 | 1.18.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/kyverno/kyverno. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/kyverno/kyverno to 1.18.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54523 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-54523 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-54523. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-54523 in your dependencies?
O3 detects CVE-2026-54523 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.