CVE-2023-5675 is a security vulnerability identified in the Quarkus framework, specifically affecting versions 3.2.0, 3.6.0, and 3.7.0. Quarkus is a popular Java framework used for building cloud-native applications, often leveraging RESTEasy Classic or Reactive JAX-RS for RESTful endpoints. The vulnerability arises when REST endpoint methods are declared in abstract Java classes or are customized via Quarkus extensions using annotation processors. Under these conditions, the framework fails to enforce authorization policies configured via 'quarkus.security.jaxrs.deny-unannotated-endpoints' or 'quarkus.security.jaxrs.default-roles-allowed' properties. These properties are intended to restrict access to endpoints by denying unannotated endpoints or enforcing default role-based access control. Due to this flaw, protected methods can be accessed without proper authorization checks, effectively bypassing security controls. The CVSS 3.1 base score is 6.5 (medium severity), reflecting that the vulnerability can be exploited remotely without authentication or user interaction, impacting confidentiality and integrity but not availability. No known exploits have been reported in the wild as of the publication date. This vulnerability is particularly critical for applications exposing sensitive data or critical business logic via REST endpoints, as unauthorized access could lead to data leakage or unauthorized operations. The issue stems from the interaction between abstract method declarations, annotation processing, and Quarkus security enforcement mechanisms, highlighting a gap in the framework's security model. Organizations using affected Quarkus versions should review their endpoint security configurations and apply patches or mitigations once available.

The primary impact of CVE-2023-5675 is unauthorized access to REST endpoints that should be protected by role-based authorization policies. For European organizations, this could lead to unauthorized disclosure of sensitive information, unauthorized modification of data, or execution of privileged operations within applications built on vulnerable Quarkus versions. Industries such as finance, healthcare, government, and critical infrastructure that rely on Java microservices for business-critical operations are at heightened risk. The vulnerability undermines the confidentiality and integrity of application data and services, potentially leading to regulatory non-compliance (e.g., GDPR violations) if personal or sensitive data is exposed. Since exploitation requires no authentication or user interaction and can be performed remotely, attackers can leverage this flaw to gain unauthorized access at scale. This could facilitate further lateral movement or escalation within affected networks. The lack of known exploits in the wild currently reduces immediate risk, but the medium severity score and ease of exploitation warrant proactive mitigation. European organizations with public-facing APIs or internal services using Quarkus should consider this a significant security concern.

To mitigate CVE-2023-5675, European organizations should: 1) Upgrade Quarkus to a patched version as soon as it becomes available from the vendor or community, ensuring the fix addresses authorization enforcement on abstract or annotated methods. 2) Review and audit all REST endpoints, especially those declared in abstract classes or customized via annotation processors, to verify that authorization annotations are correctly applied and enforced. 3) Temporarily disable or avoid using the 'quarkus.security.jaxrs.deny-unannotated-endpoints' and 'quarkus.security.jaxrs.default-roles-allowed' properties if they cannot be reliably enforced, or implement additional manual authorization checks in code. 4) Employ runtime application self-protection (RASP) or API gateways with strict access control policies to add defense-in-depth. 5) Conduct penetration testing focused on authorization bypass scenarios to detect potential exploitation. 6) Monitor application logs and network traffic for unusual access patterns to REST endpoints. 7) Educate developers about secure use of abstract classes and annotation processors in Quarkus to prevent similar issues. These steps go beyond generic patching by emphasizing configuration review, code auditing, and layered security controls.