CVE-2025-1098 is a vulnerability classified under CWE-20 (Improper Input Validation) found in the Kubernetes ingress-nginx controller, specifically in versions up to 1.12.0. The flaw stems from insufficient validation of the 'mirror-target' and 'mirror-host' annotations in Ingress resources, which are intended to configure request mirroring in nginx. An attacker with the ability to create or modify Ingress resources can exploit this to inject arbitrary nginx configuration directives. This injection can lead to arbitrary code execution within the ingress-nginx controller's process context, which runs with cluster-level privileges. Additionally, because the ingress-nginx controller typically has access to all Kubernetes Secrets in the cluster, an attacker can leverage this vulnerability to disclose sensitive information such as credentials, tokens, or certificates. The vulnerability has a CVSS 3.1 score of 8.8, indicating high severity, with an attack vector over the network, low attack complexity, requiring privileges but no user interaction, and impacting confidentiality, integrity, and availability. Although no exploits are currently known in the wild, the potential impact is significant given the widespread use of ingress-nginx in Kubernetes environments. The vulnerability highlights the risks of overly permissive access controls and the importance of input validation in Kubernetes controllers.

For European organizations, this vulnerability poses a critical risk to Kubernetes clusters running ingress-nginx, a widely adopted ingress controller in cloud-native environments. Successful exploitation can lead to full compromise of the ingress-nginx controller, enabling attackers to execute arbitrary code and access all Secrets within the cluster. This can result in data breaches, lateral movement within the cluster, disruption of services, and exposure of sensitive credentials. Organizations relying on Kubernetes for production workloads, especially those in regulated sectors such as finance, healthcare, and government, face compliance and operational risks. The ability to inject arbitrary configuration also threatens the integrity and availability of applications behind the ingress controller. Given the default broad Secret access by ingress-nginx, the impact extends beyond a single namespace, potentially compromising the entire cluster. The vulnerability is particularly concerning for multi-tenant clusters and managed Kubernetes services where ingress-nginx is deployed with default permissions.

1. Upgrade ingress-nginx to a version later than 1.12.0 as soon as a patch is released by the Kubernetes project. 2. Until a patch is available, restrict the ability to create or modify Ingress resources to trusted administrators only, minimizing the risk of malicious annotation injection. 3. Implement Kubernetes Role-Based Access Control (RBAC) policies to limit ingress-nginx controller permissions, especially restricting access to Secrets where feasible. 4. Monitor Ingress resource annotations for suspicious or unexpected values, particularly 'mirror-target' and 'mirror-host'. 5. Employ network segmentation and firewall rules to limit exposure of the ingress-nginx controller to untrusted networks. 6. Use admission controllers or validating webhooks to enforce strict validation of Ingress annotations to prevent injection of arbitrary configuration. 7. Regularly audit Kubernetes cluster configurations and Secrets access to detect potential misuse. 8. Consider deploying ingress-nginx with reduced privileges or in a sandboxed environment to limit the blast radius of a compromise.