EEF-CVE-2026-48599
Authorization bypass via path binding override in elixir-grpc/grpc HTTP transcoding
Details
## Summary
Authorization Bypass Through User-Controlled Key vulnerability in elixir-grpc grpc allows authenticated attackers to access or modify resources belonging to other users by smuggling a conflicting value for any path-bound field via the query string or request body.
In 'Elixir.GRPC.Server.Transcode':map\_request/5 (lib/grpc/server/transcode.ex), all three clauses use Map.merge/2 with path bindings as the first argument, giving them the lowest merge precedence. A request such as GET /users/me/profile?user\_id=victim (or a POST with {"user\_id": "victim"} when body: "\*") yields a decoded protobuf struct where the path-bound field carries the attacker-supplied value rather than the router-extracted value. Any handler that uses the path-bound field for authorization, multi-tenancy scoping, or ownership checks is silently bypassed.
This issue affects grpc from 0.8.0 before 1.0.0.
## Configuration
HTTP-to-gRPC transcoding must be enabled.
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