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Fencer Intel
high 7.6

CVE-2026-124278 json

Path bindings ignored for gRPC Content-Types on transcoded routes in elixir-grpc grpc_server

published yesterday modified yesterday also EEF-CVE-2026-124278 , EUVD-2026-125537 , GHSA-xc5v-89vq-hv5m

cvss
7.6
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 43%
public exploits
0
none known

Summary

Authorization Bypass Through User-Controlled Key vulnerability in elixir-grpc grpc_server and grpc allows an attacker to make a handler act on a resource other than the one named in the URL of an HTTP-transcoded route, via a request with a gRPC Content-Type.

Only the transcoding clause of GRPC.Server.do_handle_request/4 (grpc_server/lib/grpc/server.ex, and lib/grpc/server.ex before the package split) applies the route's path bindings to the request message. The Cowboy handler picks that clause from the request Content-Type, not from the route. A request to a transcoded URL with application/grpc or application/grpc-web is decoded from the body alone, so every path-bound field takes its value from the body. A gateway, proxy rule or WAF that authorizes on the URL path sees one resource while the handler receives another.

This issue affects grpc_server: from 1.0.0 before 1.1.0; grpc: from 0.8.0 before 1.0.0.

Patch / fix

  • hex grpc_server 1.1.0
  • hex grpc 1.0.0
  • elixir-grpc grpc_server 1.1.0
  • elixir-grpc grpc 1.0.0

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Exploit prediction

0.50% chance of exploitation in the next 30 days, higher than 43% of all scored CVEs (FIRST EPSS, 2026-11-14).

CVSS scores

assigned by version score vector
CNA 4.0 7.6 CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CNA 4.0 7.6 CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem package affected fixed in
hex grpc_server
>=1.0.0, <1.1.0
1.1.0
hex grpc
>=0.8.0, <1.0.0
1.0.0

Affected products

  • elixir-grpc grpc_server
  • elixir-grpc grpc

Classification

Weakness
  • CWE-436 Interpretation Conflict
  • CWE-639 Authorization Bypass Through User-Controlled Key

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of elixir-grpc/grpc published their own advisory on GitHub. Reviewed sources take precedence over it.