CVE
Authorization bypass in HTTP-transcoded routes
Affects grpc_server 1.0.0 before 1.1.0 and grpc 0.8.0 before 1.0.0 when HTTP-to-gRPC transcoding is enabled and URL-path access checks sit in front of the server. Fixed in grpc_server 1.1.0 and grpc 1.0.0.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in grpc_server 1.1.0 · grpc 1.0.0
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. HTTP-to-gRPC transcoding is enabled (http_transcode: true). Access to the resource is decided from the URL path by a gateway, proxy rule or WAF in front of the server. Affected versions: grpc_server 1.0.0 before 1.1.0, and grpc 0.8.0 before 1.0.0.
- Published
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 26/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
The elixir-grpc grpc_server and grpc packages let an attacker with low-privilege access over the network make a handler act on a resource other than the one named in the URL of an HTTP-transcoded route. By sending a request with a gRPC Content-Type, the attacker supplies the resource identifier in the message body, which bypasses gateways or WAFs that authorize based on the URL path.
Read the original description
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.
Who should check
Elixir services using grpc_server 1.0.0 to before 1.1.0 or grpc 0.8.0 to before 1.0.0 with http_transcode: true behind a URL-path-based gateway, proxy or WAF.
Read the source excerpt
“This issue affects grpc_server: from 1.0.0 before 1.1.0; grpc: from 0.8.0 before 1.0.0.”
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure8/25Specific setups only, reachable over the network
- Reach10/20Affects Hex packages
- Severity7.6/10CVSS 7.6
- No patch0/5No signal
What would change the score
- Would score about 76 if added to CISA KEV
- Would score about 71 if CISA's SSVC rates exploitation active
- Would score about 33 if CISA's SSVC rates it automatable
What to do
Check whether your setup matches what the bug needs.
HTTP-to-gRPC transcoding is enabled (http_transcode: true). Access to the resource is decided from the URL path by a gateway, proxy rule or WAF in front of the server. Affected versions: grpc_server 1.0.0 before 1.1.0, and grpc 0.8.0 before 1.0.0.Upgrade to a fixed version: grpc_server 1.1.0 · grpc 1.0.0.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-124278 (Path bindings ignored for gRPC Content-Types on transcoded routes in elixir-grpc grpc_server), using the cve.now data below.
Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.
What cve.now has for CVE-2026-124278 (entry last updated 2026-11-13):
Affected:
- Hex package grpc_server: from 1.0.0, fixed in 1.1.0
- elixir-grpc grpc_server: version range not reported
- Hex package grpc: from 0.8.0, fixed in 1.0.0
- elixir-grpc grpc: version range not reported
- Hex package grpc_server: from 1.0.0, fixed in 1.1.0
- Hex package grpc: from 0.8.0, fixed in 1.0.0
Fixed versions: 1.1.0, 1.0.0.
Vendor patches: 953ab98 (source: https://github.com/elixir-grpc/grpc/security/advisories/GHSA-xc5v-89vq-hv5m). Check each asset for these patch ids, not only its version.
Conditions (all must be true for the bug to be hit):
- HTTP-to-gRPC transcoding is enabled (http_transcode: true). (source: https://github.com/elixir-grpc/grpc/security/advisories/GHSA-xc5v-89vq-hv5m)
- Access to the resource is decided from the URL path by a gateway, proxy rule or WAF in front of the server. (source: https://github.com/elixir-grpc/grpc/security/advisories/GHSA-xc5v-89vq-hv5m)
- Affected versions: grpc_server 1.0.0 before 1.1.0, and grpc 0.8.0 before 1.0.0. (source: https://github.com/elixir-grpc/grpc/security/advisories/GHSA-xc5v-89vq-hv5m)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: network access, low-privilege login, no user action.
CISA KEV: CVE-2026-124278 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-124278 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Packages (Hex): find every lockfile in each project and run the stack.check operation of the cve.now MCP server (execute) on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/elixir-grpc/grpc/security/advisories/GHSA-xc5v-89vq-hv5m
- https://github.com/elixir-grpc/grpc/commit/953ab980d8a127e895d3ab9505fc4b9337bb32f7
- https://cna.erlef.org/cves/CVE-2026-124278.html
- https://osv.dev/vulnerability/EEF-CVE-2026-124278
- https://github.com/elixir-grpc/grpc/commit/0332faae5f5e132314794dbfdae5edecbccea292
- https://github.com/elixir-grpc/grpc/commit/8aaf3d3a8c4c7b08ac65e9c6f254e0d24da1d048
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-124278
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-124278"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- grpc_serverHex
From 1.0.0 · fixed in 1.1.0
- elixir-grpc/grpc
Version range not reported
- grpcHex
From 0.8.0 · fixed in 1.0.0
- elixir-grpc/grpc
Version range not reported
- grpc_serverHex
From 1.0.0 · fixed in 1.1.0
- grpcHex
From 0.8.0 · fixed in 1.0.0
Evidence 8
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-124278
Is CVE-2026-124278 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
With HTTP-to-gRPC transcoding enabled, path bindings are ignored for gRPC Content-Types on transcoded routes. An attacker whose requests are authorized by URL path can make the handler read or modify a resource the path does not name, such as another tenant's data.Source: github.com
Which versions are affected by CVE-2026-124278?
grpc_server (Hex): from 1.0.0 before 1.1.0. grpc (Hex): from 0.8.0 before 1.0.0. grpc_server (Hex): from 1.0.0 before 1.1.0. grpc (Hex): from 0.8.0 before 1.0.0.Source: cve.now feed data
Am I affected, and how do I check?
The affected versions are grpc_server 1.0.0 before 1.1.0 and grpc 0.8.0 before 1.0.0. The setup involves http_transcode: true, with access decided from the URL path by a gateway, proxy rule or WAF in front of the server. To check, look at the installed grpc_server and grpc versions in mix.lock and at the http_transcode setting.Source: github.com
How do I fix CVE-2026-124278?
Upgrade grpc_server to 1.1.0 or grpc to 1.0.0. The vendor's patch id for this fix is 953ab98.Source: github.com