CVE-2025-1097 is a vulnerability identified in the Kubernetes ingress-nginx controller, specifically affecting versions up to 1.12.0. The root cause is improper input validation (CWE-20) of the 'auth-tls-match-cn' Ingress annotation, which is intended to specify client certificate common names for TLS authentication. An attacker with limited privileges can craft malicious Ingress resources that inject arbitrary configuration directives into the nginx configuration managed by the ingress-nginx controller. This injection can lead to arbitrary code execution within the controller's process context, which runs with cluster-level permissions. Furthermore, since the ingress-nginx controller typically has access to all Kubernetes Secrets cluster-wide by default, exploitation can result in unauthorized disclosure of sensitive data such as credentials, tokens, or certificates stored as Secrets. The vulnerability is remotely exploitable over the network without user interaction but requires some level of privileges (PR:L) to create or modify Ingress resources. Although no active exploits have been reported, the potential impact is significant due to the combination of code execution and sensitive data exposure. The vulnerability was reserved in early February 2025 and published in late March 2025, with a CVSS v3.1 score of 8.8, indicating high severity. No official patches were linked at the time of reporting, but remediation is expected in future ingress-nginx releases. The issue highlights the risks of insufficient input validation in Kubernetes controllers and the importance of least privilege principles in RBAC configurations.

For European organizations, the impact of CVE-2025-1097 is substantial. Many enterprises and public sector entities in Europe rely heavily on Kubernetes for cloud-native application deployment, with ingress-nginx being one of the most popular ingress controllers. Successful exploitation could allow attackers to execute arbitrary code within the ingress-nginx controller, potentially leading to full cluster compromise. The disclosure of Secrets could expose sensitive credentials, private keys, and tokens, undermining confidentiality and enabling further lateral movement or privilege escalation. This is particularly critical for sectors such as finance, healthcare, and government, where data protection regulations like GDPR impose strict requirements on data confidentiality and breach notification. The availability of services could also be disrupted if attackers manipulate ingress configurations or cause controller failures. Given the default broad Secret access by the controller, organizations that have not implemented strict RBAC policies or network segmentation are at higher risk. The threat also raises concerns about supply chain security and cloud infrastructure integrity across European cloud providers and enterprises.

1. Upgrade ingress-nginx to a version later than 1.12.0 as soon as a patched release is available to address CVE-2025-1097. 2. Implement strict RBAC policies to minimize the ingress-nginx controller's access to Kubernetes Secrets, limiting it to only those necessary for operation rather than cluster-wide access. 3. Enforce validation and sanitization of Ingress annotations, particularly 'auth-tls-match-cn', through admission controllers or policy enforcement tools like OPA Gatekeeper or Kyverno to prevent injection of malicious configuration. 4. Monitor Kubernetes API server logs and ingress-nginx controller logs for suspicious creation or modification of Ingress resources with unusual annotation values. 5. Use network policies to restrict access to the ingress-nginx controller and limit exposure to untrusted networks. 6. Conduct regular security audits and penetration testing focused on Kubernetes ingress configurations and controller privileges. 7. Educate DevOps and security teams about the risks of annotation injection and the importance of least privilege principles in Kubernetes environments.