What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.6 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-15 · updated 2026-10-25
• Weakness: CWE-639

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.

Affected products

• elixir-grpc grpc: from 0.8.0 before 1.0.0 — fixed in 1.0.0

How to fix

Upgrade to a fixed version: elixir-grpc grpc 1.0.0. Check the vendor advisory for mitigations.

References

• https://cna.erlef.org/cves/CVE-2026-48599.html
• https://github.com/elixir-grpc/grpc/commit/33b6a095dbc91c6dee3c7b90893d7d74952e82e4
• https://github.com/elixir-grpc/grpc/commit/8aaf3d3a8c4c7b08ac65e9c6f254e0d24da1d048
• https://github.com/elixir-grpc/grpc/security/advisories/GHSA-mwr4-5g34-j5cq
• https://osv.dev/vulnerability/EEF-CVE-2026-48599
• https://github.com/elixir-grpc/grpc/security/advisories/GHSA-mwr4-5g34-j5cq

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