HighCVE-2026-124278

    Path bindings ignored for gRPC Content-Types on transcoded routes in elixir-grpc grpc_server (CVE-2026-124278)

    Published Last modified Sources: CVE.org, OSV, EUVD

    Share

    What is affected, what to do

    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.

    Update Elixir-grpc Grpc Server to version 1.1.0, Elixir-grpc Grpc to version 1.0.0.

    Affected
    • Elixir-grpc Grpc Server lt 1.0.0..1.1.0
    • Elixir-grpc Grpc lt 0.8.0..1.0.0
    Fixed in
    • Elixir-grpc Grpc Server 1.1.0
    • Elixir-grpc Grpc 1.0.0

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    7.6

    XIEM Effective CVSS

    Highest available CVSS rating from NVD and vendor data.

    Source: Vendor (CNA), CVSS v4

    7.6

    CVSS v4

    Severity High on the scale from 0 to 10.

    Source: CVE.org, OSV, EUVD

    —

    EPSS score

    No value is available for this vulnerability.

    Show all metrics
    Severity
    High
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    68.00 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    7.6 Methodology
    CVSS v4

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    7.6
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-436, CWE-639

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    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.

    Source: cvelistv5, OSV (Open Source Vulnerabilities), ENISA EUVD, NVD (NIST), CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    elixir-grpcgrpc
    • 0.8.0 – < 1.0.0
    • 1.0.0
    elixir-grpcgrpc_server
    • 1.0.0 – < 1.1.0
    • 1.1.0
    hexgrpc
    • 0.11.1
    • 0.10.1
    • 0.11.0
    • 0.8.1
    • 0.11.5
    • 0.10.0
    • 0.9.0
    • 0.11.2
    • 0.11.3
    • 0.11.4
    • 0.10.2
    • 1.0.0-rc.1
    • 0.8.0
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • 1.0.0
    hexgrpc_server
    • 1.0.3
    • 1.0.2
    • 1.0.6
    • 1.0.0
    • 1.0.1
    • 1.0.5
    • 1.0.4
    • —
    • —
    • —
    • 1.1.0
    • —
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-436Interpretation Conflict

      Class

      Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B's state.

      Entry at MITRE CWE-436

    • CWE-639Authorization Bypass Through User-Controlled Key

      Base

      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.

      Entry at MITRE CWE-639

    References & sources

    • github.comPath bindings ignored for gRPC Content-Types on transcoded routes in elixir-grpc grpc_serveradvisory, Vendor advisory, related, euvd
    • cna.erlef.orgEEF CNA record for CVE-2026-124278web, related, euvd
    • github.comIntroducing commit 0332faa in elixir-grpc/grpcweb, related, euvd
    • github.comFix commit 953ab98 in elixir-grpc/grpcfix, Patch, euvd
    • github.comIntroducing commit 8aaf3d3 in elixir-grpc/grpcweb, related, euvd
    • hex.pmpackages/grpc_serverpackage
    • hex.pmpackages/grpcpackage
    • OSV (Open Source Vulnerabilities)OSV record EEF-CVE-2026-124278related, euvd

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. ReceivedEEF

      CVSS V4.0: AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

      Weakness type: CWE-436, CWE-639

      Description added or changed

      Show 11 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      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.
      CVSSadded
      —
      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
      Weakness type (CWE)added
      —
      CWE-436
      Weakness type (CWE)added
      —
      CWE-639
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/124xxx/CVE-2026-124278.json">CVE-2026-124278</a>
      Referenceadded
      —
      https://cna.erlef.org/cves/CVE-2026-124278.html
      Referenceadded
      —
      https://github.com/elixir-grpc/grpc/commit/0332faae5f5e132314794dbfdae5edecbccea292
      Referenceadded
      —
      https://github.com/elixir-grpc/grpc/commit/8aaf3d3a8c4c7b08ac65e9c6f254e0d24da1d048
      Referenceadded
      —
      https://github.com/elixir-grpc/grpc/commit/953ab980d8a127e895d3ab9505fc4b9337bb32f7
      Referenceadded
      —
      https://github.com/elixir-grpc/grpc/security/advisories/GHSA-xc5v-89vq-hv5m
      Referenceadded
      —
      https://osv.dev/vulnerability/EEF-CVE-2026-124278

      Source identifier: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db

    Embed badge

    Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.

    Badge preview for CVE-2026-124278
    <a href="https://intel.neosec.eu/en/cve/CVE-2026-124278"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-124278.svg?lang=en" alt="CVE-2026-124278 – NEOSEC Intel" height="20"></a>