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High, CVSS 8.1amended

Next.js has a Middleware / Proxy bypass through dynamic route parameter injection

CVE-2026-44574GHSA-492v-c6pp-mqqv

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (next 16.2.5, 15.5.16), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • npm next

    Affected
    >= 15.4.0, < 15.5.16>= 16.0.0, < 16.2.5
    Fixed in
    16.2.5, 15.5.16

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
8.1 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
EPSS
  • CVE-2026-44574: 0.64% estimated exploitation activity in the next 30 days; percentile 50.55 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Impact Applications that rely on middleware to protect dynamic routes can be vulnerable to authorization bypass. In affected deployments, specially crafted query parameters can alter the dynamic route value seen by the page while leaving the visible path unchanged, which can allow protected content to be rendered without passing the expected middleware check. Fix We now only honor internal route-parameter normalization in trusted routing flows and ignore externally supplied parameter encodings that should never have been accepted from ordinary requests. Workarounds If you cannot upgrade immediately, enforce authorization in route or page logic instead of relying solely on middleware path matching.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-492v-c6pp-mqqv

  2. Revision 1 · created ·

    Published from osv record GHSA-492v-c6pp-mqqv

Agent brief

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# Patch Next advisory brief: CVE-2026-44574

Advisory: Next.js has a Middleware / Proxy bypass through dynamic route parameter injection
IDs: CVE-2026-44574, GHSA-492v-c6pp-mqqv
Record: https://patchnext.com/advisories/cve-2026-44574 (revision 2, source checked 26 Oct 2026, 12:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: next 16.2.5, 15.5.16. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm next: affected >= 15.4.0, < 15.5.16; >= 16.0.0, < 16.2.5; fixed in 16.2.5, 15.5.16

## Suggested inspection (read-only)
- `npm ls next --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on next.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-492v-c6pp-mqqv (OSV record GHSA-492v-c6pp-mqqv lists affected ranges: npm next >=15.4.0 =16.0.0 <16.2.5 (fixed))
- Verified: https://github.com/advisories/GHSA-492v-c6pp-mqqv (GitHub-reviewed advisory GHSA-492v-c6pp-mqqv lists affected ranges: npm next >=15.4.0 =16.0.0 <16.2.5)

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