CVE-2026-9495: @koa/router @koa/router Has An Access Control Vulnerability

MODERATE
Advisory Identifier: GHSA-47p6-69vm-vw6v
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CVSS 7.3
CWE-284
Published
Advisory Summary

CVE-2026-9495 is a MODERATE (CVSS 7.3) @koa/router has an access control vulnerability (CWE-284: Improper Access Control) affecting @koa/router libraries in the npm ecosystem. The issue involves @koa/router has an access control bypass. Remediation is available by upgrading affected packages to version 15.0.0.

CVE-2026-9495 at a Glance

CVE Identifier CVE-2026-9495
GHSA Identifier GHSA-47p6-69vm-vw6v
Severity MODERATE
CVSS v3.1 Base Score 7.3
CWE Classification CWE-284: Improper Access Control
Affected Product @koa/router
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2026-9495

To remediate this vulnerability, upgrade all affected @koa/router dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

@koa/router fixed: 15.0.0 
npm install @koa/router@15.0.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls @koa/router

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-9495, inspect your project dependencies using npm:

npm ls @koa/router

Analyze the terminal output to locate any version of @koa/router in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 15.0.0), your application is affected.

Note: The npm ls @koa/router command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-284: Improper Access Control, where the product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. In @koa/router, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

Versions of the package @koa/router from 14.0.0 and before 15.0.0 are vulnerable to Access Control Bypass due to the middleware being silently dropped from the execution chain when the router prefix contains path parameters. Depending on what the skipped middleware was supposed to protect, an attacker could bypass authentication and authorization, evade rate limiting or bypass input sanitization.

CVE-2026-9495 Affected @koa/router Versions

1 component(s)
Fixed Versions:
15.0.0
Product / Package Ecosystem Affected Versions Fixed Version
@koa/router
npm/@koa/router
npm
≥ 14.0.0
< 15.0.0
15.0.0

References

NVD — CVE-2026-9495 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-9495
@koa/router Source Repository REPOSITORY
https://github.com/koajs/router/issues/202
@koa/router Source Repository REPOSITORY
https://github.com/koajs/router/pull/206
Security Fix Commit FIX COMMIT
https://github.com/koajs/router/commit/d53e17f284557b1f417946f9807ee52290c3c759
@koa/router Source Repository REPOSITORY
https://github.com/koajs/router
@koa/router Security Information SECURITY
https://security.snyk.io/vuln/SNYK-JS-KOAROUTER-12215044

Frequently Asked Questions

What is CVE-2026-9495?
CVE-2026-9495 is a security vulnerability in @koa/router involving @koa/router has an Access Control Bypass under CWE-284: Improper Access Control.
Which @koa/router versions are affected?
Affected versions include releases prior to 15.0.0 across affected packages: @koa/router.
What version fixes CVE-2026-9495?
Upgrading to 15.0.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is @koa/router affected?
Yes, @koa/router is affected in releases prior to 15.0.0. Upgrade your dependency to 15.0.0 or later.
What is the CVSS score of CVE-2026-9495?
CVE-2026-9495 has a CVSS v3.1 base score of 7.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L.
What CWE is associated with CVE-2026-9495?
CVE-2026-9495 is classified under CWE-284: Improper Access Control (The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.).
How can I check npm dependencies for CVE-2026-9495?
Run the dependency tree command: 'npm ls @koa/router'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-47p6-69vm-vw6v",
  "modified" : "2026-06-30T17:39:43Z",
  "published" : "2026-05-26T13:30:54Z",
  "aliases" : [ "CVE-2026-9495" ],
  "summary" : "@koa/router has an Access Control Bypass",
  "details" : "Versions of the package @koa/router from 14.0.0 and before 15.0.0 are vulnerable to Access Control Bypass due to the middleware being silently dropped from the execution chain when the router prefix contains path parameters. Depending on what the skipped middleware was supposed to protect, an attacker could bypass authentication and authorization, evade rate limiting or bypass input sanitization.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@koa/router"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "14.0.0"
      }, {
        "fixed" : "15.0.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-9495"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/koajs/router/issues/202"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/koajs/router/pull/206"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/koajs/router/commit/d53e17f284557b1f417946f9807ee52290c3c759"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/koajs/router"
  }, {
    "type" : "WEB",
    "url" : "https://security.snyk.io/vuln/SNYK-JS-KOAROUTER-12215044"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-284" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-30T17:39:43Z",
    "nvd_published_at" : "2026-05-26T07:16:19Z"
  }
}