CVE-2025-1097 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 issue stems from insufficient validation of the `auth-tls-match-cn` annotation used in Ingress resources. This annotation can be manipulated to inject arbitrary configuration directives into the nginx configuration managed by the ingress controller. Because the ingress-nginx controller runs with elevated privileges and has access to all Kubernetes Secrets by default, an attacker exploiting this vulnerability can execute arbitrary code within the controller's context. This can lead to full compromise of the ingress-nginx pod, unauthorized disclosure of sensitive Secrets, and potentially lateral movement within the cluster. The attack vector requires the ability to create or modify Ingress resources, which implies some level of cluster access or compromised credentials. No user interaction is needed, and the vulnerability can be exploited remotely over the network. The CVSS v3.1 score is 8.8 (high), reflecting the ease of exploitation (low attack complexity), the requirement for privileges (PR:L), and the severe impact on confidentiality, integrity, and availability. No known exploits are reported in the wild yet, but the potential impact justifies urgent mitigation. The vulnerability highlights the risks of default broad Secret access by the ingress controller and the need for strict input validation in Kubernetes resource annotations.

For European organizations, this vulnerability poses a critical threat to Kubernetes-based infrastructure, especially those relying on ingress-nginx for managing external access to services. Exploitation can lead to unauthorized disclosure of sensitive data stored in Kubernetes Secrets, including credentials, certificates, and tokens, potentially compromising entire clusters. Arbitrary code execution within the ingress controller can disrupt service availability, enable persistent backdoors, or facilitate lateral movement to other cluster components. This risk is particularly acute for sectors with stringent data protection requirements such as finance, healthcare, and government, where breaches could lead to regulatory penalties under GDPR and other frameworks. Organizations using multi-tenant clusters or exposing ingress management to multiple teams face increased risk due to the attack vector requiring Ingress resource modification privileges. The vulnerability also threatens cloud service providers and managed Kubernetes platforms operating in Europe, as compromise could impact multiple customers. Overall, the impact encompasses confidentiality breaches, integrity violations, and denial of service, with potential cascading effects on business operations and trust.

1. Upgrade ingress-nginx to a patched version beyond 1.12.0 as soon as it becomes available to eliminate the vulnerability. 2. Restrict RBAC permissions to limit which users or service accounts can create or modify Ingress resources, minimizing the attack surface. 3. Implement admission controllers or policy enforcement tools (e.g., OPA Gatekeeper) to validate and sanitize Ingress annotations, preventing malicious configuration injection. 4. Reduce the ingress-nginx controller's access to Kubernetes Secrets by applying the principle of least privilege, using Kubernetes RBAC to scope Secret access narrowly rather than cluster-wide. 5. Monitor audit logs for suspicious Ingress resource changes or anomalous annotation values indicative of exploitation attempts. 6. Employ network segmentation and isolate ingress controllers to limit lateral movement if compromised. 7. Regularly scan Kubernetes manifests and configurations for insecure annotations or misconfigurations. 8. Educate DevOps and security teams about the risks of annotation injection and enforce secure coding and deployment practices for Kubernetes resources.