CVE-2026-48599 – Authorization bypass via path binding override in elixir-grpc/grpc HTTP transcoding

CVE ID :CVE-2026-48599

Published : June 15, 2026, 11:16 p.m. | 25 minutes ago

Description :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.

Severity: 7.6 | HIGH

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