Findings

CVE-2026-84199

Kyverno APICall SSRF Vulnerability Leading to Multi-Tenant Isolation Breach in github.com/kyverno/kyverno

Published Apr 14, 2026 · updated Oct 14, 2026

### Summary Kyverno's APICall feature contains a Server-Side Request Forgery (SSRF) vulnerability that allows users with Policy creation permissions to access arbitrary internal resources through Kyverno's high-privilege ServiceAccount. In multi-tenant Kubernetes environments, this constitutes a classic Confused Deputy problem: low-privilege tenants can steal sensitive data from other tenants (such as database passwords and API keys) and cloud platform IAM credentials, completely breaking tenant isolation. This vulnerability does not require cluster-admin privileges and can be exploited with only namespace-level Policy creation permissions. ### Details #### Vulnerability Mechanism Kyverno's APICall feature allows Policies to fetch external data via HTTP requests. This feature does not validate target URLs when executing HTTP requests, leading to an SSRF vulnerability. **Source Point - User-Controlled URL** File: , lines 247-250 The URL field is completely controlled by users through Policy configuration, with no validation mechanism to restrict target addresses. **Sink Point - HTTP Request Execution** File: , lines 65-110 Line 80's directly executes the HTTP request without checking if the target URL is an internal IP address (like 169.254.169.254) or resources belonging to other tenants. **Confused Deputy Problem** In multi-tenant environments, Kyverno uses a cluster-wide high-privilege ServiceAccount to execute all APICall requests. When a low-privilege tenant creates a Policy containing malicious APICall directives, Kyverno executes these requests with its own high privileges, leading to privilege escalation. Attack path: ### PoC #### Environment Setup **Prerequisites** - Kubernetes cluster - Kyverno v1.16.0 installed - Mock cloud metadata service (optional, for testing cloud credential theft) **Step 1: Install Kyverno** Verify installation: **Step 2: Deploy Mock Metadata Service** Create file : Deploy: **Step 3: Create Multi-Tenant Environment** Create two tenan