CVE-2026-48599 Authorization bypass via path binding override in elixir-grpc/grpc HTTP transcoding
Authenticated attackers can bypass authorization checks in Elixir gRPC services by overriding path-bound fields via query strings or request bodies.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-48599?
CVE-2026-48599 is a high-severity authentication bypass vulnerability in elixir-grpc grpc, published on 15 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-639
Which versions are affected by CVE-2026-48599?
3 open source packages ship an affected version, including grpc.
| Package | Affected | Fixed in |
|---|---|---|
grpc Hex | From 0.8.0 | 1.0.0 |
grpc Hex | From 0.8.0 | 1.0.0 |
grpc Hex | From 0.8.0 | 1.0.0 |
How do I fix CVE-2026-48599?
Upgrade grpc to 1.0.0 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-48599 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-48599 exists.
Sources
Also known as EEF-CVE-2026-48599, GHSA-mwr4-5g34-j5cq.