elixir-grpc 0.x Any transcode.ex authorization

Summaryinfo

A vulnerability marked as critical has been reported in elixir-grpc grpc 0.x. This affects an unknown function of the file lib/grpc/server/transcode.ex of the component Any Handler. Performing a manipulation results in authorization. This vulnerability was named CVE-2026-48599. The attack may be initiated remotely. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, was found in elixir-grpc grpc 0.x. This affects an unknown code of the file lib/grpc/server/transcode.ex of the component Any Handler. The manipulation with an unknown input leads to a authorization vulnerability. CWE is classifying the issue as CWE-639. The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

The weakness was presented by Peter Ullrich and Jonatan Männchen as GHSA-mwr4-5g34-j5cq. It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-48599 since 05/22/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 1.0.0 eliminates this vulnerability. Applying the patch 33b6a095dbc91c6dee3c7b90893d7d74952e82e4 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-37013). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

• elixir-grpc

Name

• grpc

Version

• 0.x

License

• open-source

Website

• Product: https://github.com/elixir-grpc/grpc/

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Be aware that VulDB is the high quality source for vulnerability data.

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