React Router vulnerable to DoS via unbounded path expansion in __manifest endpoint

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-42342: 0.30% estimated exploitation activity in the next 30 days; percentile 22.69 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

There exists a potential DOS attack vector in React Router Framework Mode applications (as well as Remix v2.10.0 - 2.17.4). Certain requests can be crafted to consume disproportionate resources on the server, resulting in response time degredation and/or service unavailability for end users. [!NOTE] This does not impact your React Router application if you are using Declarative Mode (<BrowserRouter) or Data Mode (createBrowserRouter/<RouterProvider).

Published by the source

3 Jun 2026, 21:05 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:52 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-8x6r-g9mw-2r78

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-8x6r-g9mw-2r78

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# Patch Next advisory brief: CVE-2026-42342

Advisory: React Router vulnerable to DoS via unbounded path expansion in __manifest endpoint
IDs: CVE-2026-42342, GHSA-8x6r-g9mw-2r78
Record: https://patchnext.com/advisories/cve-2026-42342 (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 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: react-router 7.15.0; @remix-run/server-runtime 2.17.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm react-router: affected >= 7.0.0, < 7.15.0; fixed in 7.15.0
- npm @remix-run/server-runtime: affected >= 2.10.0, < 2.17.5; fixed in 2.17.5

## Suggested inspection (read-only)
- `npm ls react-router --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @remix-run/server-runtime --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 react-router, @remix-run/server-runtime.
- 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-8x6r-g9mw-2r78 (OSV record GHSA-8x6r-g9mw-2r78 lists affected ranges: npm react-router >=7.0.0 =2.10.0 <2.17.5 (fixed))
- Verified: https://github.com/advisories/GHSA-8x6r-g9mw-2r78 (GitHub-reviewed advisory GHSA-8x6r-g9mw-2r78 lists affected ranges: npm react-router >=7.0.0 =2.10.0 <2.17.5)

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