CVE-2026-122313 in Kyverno
Summary
by MITRE • 11/05/2026
Kyverno from 1.17.0 before 1.19.2 contains a privilege escalation vulnerability that allows namespace-scoped tenants to modify resources in other namespaces through NamespacedMutatingPolicy targetMatchConstraints.expression CEL output lacking namespace checks. Attackers can emit a literal target such as another tenant's RoleBinding, which the cluster-wide background controller then mutates to add attacker subjects or alter Roles, NetworkPolicies, and ConfigMaps.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 11/05/2026
The vulnerability identified in Kyverno versions prior to 1.19.2 represents a critical privilege escalation flaw rooted in the improper handling of namespace-scoped mutating policies. Specifically, the issue arises from the lack of explicit namespace validation within the Common Expression Language CEL output used by NamespacedMutatingPolicy targetMatchConstraints. In Kubernetes environments, Kyverno operates as an admission controller that enforces security and compliance policies on resources entering or being modified in a cluster. When administrators define namespaced mutating policies, they intend for these rules to apply only to resources within specific namespaces where the policy is defined. However, due to this implementation oversight, the CEL expressions used to match targets do not inherently restrict their scope to the namespace of the policy itself. This architectural gap allows attackers who have access to a single tenant's namespace to craft malicious policies that bypass intended boundaries and affect resources across the entire cluster.
From an operational perspective, this flaw enables lateral movement within a Kubernetes cluster by allowing lower-privileged users to escalate their privileges significantly. An attacker with write permissions in any namespace can create or modify a NamespacedMutatingPolicy that utilizes CEL expressions without proper namespace checks. By emitting a literal target reference pointing to resources such as RoleBindings, NetworkPolicies, ConfigMaps, or Roles located in other namespaces, the attacker forces the cluster-wide background controller to mutate these external resources. For instance, an attacker could alter a RoleBinding in a production namespace to grant themselves elevated privileges, effectively becoming a cluster administrator. Similarly, they might modify network policies to disrupt service connectivity for critical applications or tamper with configuration maps that control application behavior, leading to potential data exfiltration or denial of service conditions across the infrastructure.
This vulnerability aligns closely with CWE-269 Improper Privilege Management and CWE-787 Out-of-bounds Write in terms of its impact on system integrity and access controls. In the context of the MITRE ATT&CK framework for Kubernetes, this behavior corresponds to techniques involving privilege escalation through misconfigured admission controllers or policy engines. The attack vector leverages the trust placed in namespaced resources by assuming they cannot affect global state, which is a fundamental security assumption violated here. The exploitation does not require initial cluster-admin privileges; instead, it relies on standard user permissions within any namespace, making it particularly dangerous in multi-tenant environments where isolation between tenants is paramount for security and compliance requirements such as SOC2 or ISO 27001.
To mitigate this risk, organizations must immediately upgrade Kyverno to version 1.19.2 or later, where the issue has been addressed by enforcing stricter namespace scoping in CEL evaluations within mutating policies. Until an upgrade is feasible, administrators should implement strict RBAC controls to limit who can create or modify MutatingPolicy resources across all namespaces. Additionally, adopting a principle of least privilege for service accounts and users involved with policy management reduces the attack surface. Security teams should also audit existing Kyverno configurations to identify any namespaced mutating policies that utilize complex CEL expressions targeting cluster-wide resources, ensuring that such patterns are removed or restricted. Regular monitoring of admission controller logs can help detect anomalous mutation attempts that target resources outside their originating namespace, providing an early warning mechanism for potential exploitation attempts.