Description

A vulnerability has been found in LogNet grpc-spring-boot-starter up to 5.2.0. Affected is an unknown function of the component Annotation Processing. Such manipulation leads to improper authorization. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is told to be difficult. The exploit has been disclosed to the public and may be used. The project was informed of the problem early through an issue report but has not responded yet.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "5.0",
  "pubDate": "2026-08-31T00:16:41.800Z",
  "pubdate": "2026-08-31T00:16:41.800Z",
  "executiveSummary": "A critical security vulnerability has been identified within the LogNet grpc-spring-boot-starter library, specifically affecting versions up to and including 5.2.0. The vulnerability pertains to the Annotation Processing component, which fails to correctly enforce authorization logic. This oversight results in a flaw categorized as improper authorization, potentially allowing unauthorized actors to bypass security constraints.\nThe vulnerability is remotely exploitable, posing a significant risk to applications that rely on this library for gRPC service management. While the exploitability is classified as difficult and the attack requires a high level of complexity, the existence of public exploit code increases the threat profile for organizations utilizing affected versions. Successful exploitation could lead to unauthorized access to internal service methods or data, compromising the integrity and confidentiality of the affected microservices architecture. Despite early disclosure to the project maintainers, no official remediation has been issued, necessitating proactive defensive measures by developers to prevent potential exploitation.",
  "technicalDetails": "The vulnerability resides within the Annotation Processing mechanism of the LogNet grpc-spring-boot-starter library. In a standard Spring Boot gRPC integration, annotations are utilized to simplify the exposure of service methods. The root cause of this vulnerability is the improper implementation of authorization checks during the processing of these annotations. When the library parses and binds these service annotations, it fails to verify the caller's authorization context adequately before exposing or executing the associated gRPC service methods.\nThe attack flow involves a remote actor sending specifically crafted gRPC requests targeting service endpoints that rely on annotation-based security configurations. Because the Annotation Processing component does not enforce proper access control checks during the registration or dispatching phase, the library may inadvertently expose methods that were intended to be restricted. This bypass occurs because the authorization middleware, which should intercept and validate the security headers or context of the gRPC request, is either ignored or incorrectly bypassed by the underlying annotation processing logic.\nExploitation requires high complexity because the attacker must identify precisely which service methods are improperly exposed and then craft a payload that aligns with the gRPC protocol expectations of the target service. Since the vulnerability is tied to the internal mechanics of how the starter processes these annotations, an attacker might need to reverse-engineer the service definition to determine the expected Protobuf message structures. Once the target is identified, the lack of server-side authorization enforcement allows the attacker to invoke functions with the privileges of the application's service account or an unauthenticated state, depending on how the underlying Spring Security context is handled.\nThe post-exploitation impact includes unauthorized execution of service logic, which may facilitate information disclosure, data manipulation, or unauthorized administrative actions within the gRPC service ecosystem. The vulnerability is persistent as long as the affected library is in use, as the security check failure is inherent to the library's design for handling gRPC method registration. Given that public exploit information is available, the barrier to entry for a persistent attacker is lowered, despite the inherent technical difficulties in successful remote execution."
}