---
id: "CVE-2026-122303"
kind: "vulnerability"
aliases: ["CVE-2026-122303"]
title: "Kyverno: namespace tenants can overwrite resources in other namespaces"
severity: "critical"
cvss: 9.9
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["infrastructure", "kubernetes", "kyverno", "multi-tenant"]
not_affected_if: ["kyverno-1.19.2-or-later", "kyverno-below-1.17.0", "single-tenant-cluster"]
published_at: "2026-11-05T03:17:22+00:00"
first_seen_at: "2026-11-05T03:31:40+00:00"
updated_at: "2026-11-05T03:33:06+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-122303", "first_seen_at": "2026-11-05T03:31:40+00:00"}]
exploit_sources: []
---

# Kyverno: namespace tenants can overwrite resources in other namespaces

Kyverno versions 1.17.0 through 1.19.1 let a user in one namespace abuse NamespacedMutatingPolicy mutate-existing rules to make the background controller overwrite resources in other namespaces. An attacker can overwrite Secrets, Deployments or policies across the cluster.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the Kyverno version with `kubectl get deploy -n kyverno -o wide` or the image tag on the Kyverno controller.
- Look for NamespacedMutatingPolicy resources using mutate-existing with targetMatchConstraints.expression.

## Fix

- Kyverno: move to `1.19.2` or later (affected range is 1.17.0 before 1.19.2).

## Timeline

- 2026-11-05T03:31:40+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-122303

## Documents

- [advisory] Vendor advisory: github.com https://github.com/kyverno/kyverno/security/advisories/GHSA-jcw5-3wcg-fqx5
- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/kyverno-1.17.0-before-1.19.2-cross-namespace-resource-overwrite-via-namespacedmutatingpolicy

## From the sources

Kyverno from 1.17.0 before 1.19.2 contains an authorization bypass vulnerability that allows namespace tenants to overwrite resources in other namespaces via NamespacedMutatingPolicy mutate-existing targetMatchConstraints.expression. Attackers can return a CEL map literal fabricating a target with an attacker-chosen metadata.namespace, causing the privileged background controller to overwrite Secrets, Deployments, or policies cluster-wide.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_