CVE-2022-21701 is a vulnerability affecting Istio versions 1.12.0 and 1.12.1, specifically related to an incorrect authorization issue (CWE-863) within the Kubernetes Gateway API integration, an Alpha-level feature in Istio. Istio is a widely used open-source service mesh platform designed to connect, manage, and secure microservices. The vulnerability arises because users granted the CREATE permission on the CustomResourceDefinition (CRD) gateways.gateway.networking.k8s.io can escalate their privileges to create other Kubernetes resources, such as Pods, which they would not normally have permission to create. This privilege escalation flaw is limited to the Kubernetes Gateway API resources and does not affect the Istio Gateway type (gateways.networking.istio.io), which remains secure. The issue stems from insufficient authorization checks when handling the creation of gateway resources, allowing an attacker with limited permissions to bypass intended access controls and potentially deploy arbitrary workloads within the cluster. This could lead to unauthorized code execution or lateral movement within the environment. The vulnerability only affects Istio versions from 1.12.0 up to but not including 1.12.2, and no known exploits have been reported in the wild to date. Mitigation options include upgrading to a fixed version (>=1.12.2), removing the vulnerable CRD, disabling the Gateway API deployment controller by setting the environment variable PILOT_ENABLE_GATEWAY_API_DEPLOYMENT_CONTROLLER=true in Istiod, or restricting CREATE permissions on the gateways.gateway.networking.k8s.io resource from untrusted users. These mitigations prevent exploitation by limiting the ability to create unauthorized resources or by disabling the vulnerable feature altogether.

For European organizations leveraging Istio service mesh in Kubernetes environments, this vulnerability poses a risk of privilege escalation that could lead to unauthorized deployment of workloads, potentially compromising cluster integrity and confidentiality. Attackers exploiting this flaw could create Pods or other resources, enabling them to execute arbitrary code, move laterally within the infrastructure, or disrupt service availability. This is particularly critical for organizations with multi-tenant Kubernetes clusters or those that delegate limited permissions to developers or third parties, as the vulnerability allows privilege escalation beyond intended boundaries. The impact is heightened in sectors with stringent data protection requirements such as finance, healthcare, and critical infrastructure, where unauthorized access or disruption could lead to regulatory penalties and operational downtime. Although the vulnerability affects an Alpha feature that may not be widely deployed, organizations using the Kubernetes Gateway API with Istio must assess their exposure carefully. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially given the potential for attackers to leverage this flaw in targeted attacks. Overall, the vulnerability undermines the principle of least privilege and could facilitate broader compromise within Kubernetes clusters if left unmitigated.

To effectively mitigate CVE-2022-21701, European organizations should prioritize upgrading Istio to version 1.12.2 or later, where the vulnerability is resolved. If immediate upgrade is not feasible, organizations should implement one or more of the following targeted controls: 1) Remove the gateways.gateway.networking.k8s.io CustomResourceDefinition from the cluster to eliminate the attack surface related to the Kubernetes Gateway API; 2) Disable the Gateway API deployment controller by setting the environment variable PILOT_ENABLE_GATEWAY_API_DEPLOYMENT_CONTROLLER=true in the Istiod deployment, which prevents the vulnerable component from processing gateway resources; 3) Audit and restrict RBAC policies to remove CREATE permissions on gateways.gateway.networking.k8s.io resources from untrusted or less privileged users, ensuring only highly trusted administrators retain this capability. Additionally, organizations should conduct thorough access reviews and monitor Kubernetes audit logs for suspicious creation of gateway or pod resources. Implementing network segmentation and Pod Security Policies (or equivalent admission controls) can further limit the impact of any unauthorized Pod creation. Regularly updating Kubernetes and Istio components and maintaining strict RBAC hygiene are critical to preventing exploitation of similar vulnerabilities in the future.