CVE-2026-48599

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.

Affected Software

VendorProductVersion RangeStatus
elixir-grpcgrpc0.8.0 < 1.0.0affected
elixir-grpcgrpc8aaf3d3a8c4c7b08ac65e9c6f254e0d24da1d048 < 33b6a095dbc91c6dee3c7b90893d7d74952e82e4affected

Weaknesses

  • CWE-639: CWE-639 Authorization Bypass Through User-Controlled Key

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: poc
    • Automatable: no
    • Technical Impact: total

Additional References

References