CVE-2026-4789

Summary A 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. Affected Versions - Kyverno >= 1.16.0 (with policies.kyverno.io CRDs enabled, which is the default) - Tested on: Kyverno v1.16.2 (Helm chart 3.6.2) Details The 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. Vulnerable Code: pkg/cel/libs/http/http.go func (r *contextImpl) Get(url string, headers map[string]string) (any, error) { req, err := http.NewRequestWithContext(context.TODO(), "GET", url, nil) // NO URL VALIDATION - no blocklist, no namespace restrictions ... } Contrast with resource.Lib which enforces namespace: // pkg/cel/libs/resource/lib.go func Lib(namespace string, v *version.Version) cel.EnvOption { return cel.Lib(&lib{namespace: namespace, version: v}) // Namespace enforced } This is a different code path from previously reported issues: - GHSA-8p9x-46gm-qfx2: pkg/engine/apicall/apiCall.go (URLPath) - Fixed - GHSA-459x-q9hg-4gpq: pkg/engine/apicall/executor.go (Service.URL) - Different feature (apiCall vs CEL http) - This issue: pkg/cel/libs/http/http.go (CEL http.Get/http.Post) - Not fixed PoC Tested on Kyverno v1.16.2 (Chart 3.6.2) on Kubernetes v1.35.0 (kind). A complete automated PoC script is attached. Manual steps below: 1. Setup attacker with namespace-scoped permissions kubectl create namespace attacker-ns ku

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