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CVE-2026-48599 elixir-grpc CVE debrief

CVE-2026-48599 is an Authorization Bypass Through User-Controlled Key vulnerability in elixir-grpc grpc. This vulnerability 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. The issue arises from the way 'Elixir.GRPC.Server.Transcode':map_request/5 (lib/grpc/server/transcode.ex) handles path bindings, giving them the lowest merge precedence. This results in a decoded protobuf struct where the path-bound field carries the attacker-supplied value rather than the router-extracted value, silently bypassing any handler that uses the path-bound field for authorization, multi-tenancy scoping, or ownership checks.

Vendor
elixir-grpc
Product
grpc
CVSS
HIGH 7.6
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-15
Original CVE updated
2026-06-16
Advisory published
2026-06-15
Advisory updated
2026-06-16

Who should care

Users of elixir-grpc grpc from version 0.8.0 before 1.0.0 should be aware of this vulnerability and take necessary actions to mitigate it.

Technical summary

The vulnerability is caused by the use of Map.merge/2 with path bindings as the first argument in 'Elixir.GRPC.Server.Transcode':map_request/5 (lib/grpc/server/transcode.ex), giving them the lowest merge precedence. This allows an attacker to smuggle a conflicting value for any path-bound field via the query string or request body.

Defensive priority

HIGH

Recommended defensive actions

  • Update elixir-grpc grpc to version 1.0.0 or later.
  • Review and update handlers that use path-bound fields for authorization, multi-tenancy scoping, or ownership checks.

Evidence notes

The CVE record and details can be found at [cve-org]. More information is available at [nvd]. Additional references include [ref-4], [ref-5], [ref-6], and [ref-7].

Sources and references

Verified primary and authoritative sources

  • CVE-2026-48599 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-48599

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-48599 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-48599

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Source reference

    Unverified legacy reference

    URL: https://cna.erlef.org/cves/CVE-2026-48599.html

    6b3ad84c-e1a6-4bf7-a703-f496b71e49db

  • Source reference

    Unverified legacy reference

    URL: https://github.com/elixir-grpc/grpc/commit/33b6a095dbc91c6dee3c7b90893d7d74952e82e4

    6b3ad84c-e1a6-4bf7-a703-f496b71e49db

  • Source reference

    Unverified legacy reference

    URL: https://github.com/elixir-grpc/grpc/security/advisories/GHSA-mwr4-5g34-j5cq

    6b3ad84c-e1a6-4bf7-a703-f496b71e49db

  • Source reference

    Unverified legacy reference

    URL: https://osv.dev/vulnerability/EEF-CVE-2026-48599

    6b3ad84c-e1a6-4bf7-a703-f496b71e49db

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.