Fix Shadow API Exposure in Helidon
Shadow APIs are the ghost in the machine. In Helidon, undocumented endpoints bypass your WAF rules and internal audits because they don't appear in the OpenAPI spec. This is a goldmine for attackers performing internal recon. To eliminate this exposure, you must enforce strict MicroProfile OpenAPI documentation and mandatory RBAC across all JAX-RS resources.
The Vulnerable Pattern
package com.example;import jakarta.ws.rs.*; import jakarta.ws.rs.core.Response;
@Path(“/api/v1”) public class InventoryResource { @GET @Path(“/items”) public Response getItems() { return Response.ok(“Items list”).build(); }
// SHADOW ENDPOINT: Undocumented, forgotten by dev, no security constraints. // Attackers find this via fuzzing/wordlists. @GET @Path("/debug/dump-env") public Response getEnv() { return Response.ok(System.getenv()).build(); }
}
The Secure Implementation
Stop treating security as an afterthought. To kill shadow APIs in Helidon: 1) Use MicroProfile OpenAPI annotations on every method to ensure visibility in the /openapi UI. 2) Apply class-level @RolesAllowed to ensure no 'accidental' public endpoints exist; if a dev adds a path, it is secure by default. 3) Configure Helidon's webserver to reject any route not explicitly mapped in your security provider. If it's not in the spec and doesn't have a required token, it shouldn't be reachable. Period.
package com.example;import jakarta.ws.rs.*; import jakarta.ws.rs.core.Response; import jakarta.annotation.security.RolesAllowed; import org.eclipse.microprofile.openapi.annotations.Operation; import org.eclipse.microprofile.openapi.annotations.responses.APIResponse;
@Path(“/api/v1”) @RolesAllowed(“user”) // 1. Enforce global security at class level public class SecureResource {
@GET @Path("/items") @Operation(summary = "List items", description = "Returns public inventory") @APIResponse(responseCode = "200", description = "Success") public Response getItems() { return Response.ok("Items list").build(); } @GET @Path("/admin/system-status") @RolesAllowed("admin") // 2. Restrict sensitive paths to specific roles @Operation(summary = "System Status", description = "Admin only diagnostic") public Response getStatus() { return Response.ok("Status: OK").build(); } // 3. Shadow/Debug endpoints removed from production code entirely.
}
Your Helidon API
might be exposed to Shadow API Exposure
74% of Helidon apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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