How severe is CVE-2026-42342?

CVE-2026-42342 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-42342?

CVE-2026-42342 affects the following packages: react-router (npm), @remix-run/server-runtime (npm). Ecosystems affected: npm.

How do I fix CVE-2026-42342?

Update react-router to 7.15.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42342 is resolved across your whole dependency graph.

How do I detect CVE-2026-42342 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for react-router, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-42342 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2026-42342 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-42342 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-42342?

CVE-2026-42342 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 23th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-42342?

CVE-2026-42342 is classified as Uncontrolled Resource Consumption (CWE-400). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-42342 published, and has it been updated?

CVE-2026-42342 was published on June 2, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

HIGH severity

CVE-2026-42342 — react-router

HIGH

CVE-2026-42342 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in react-router. A fix is available for react-router — see the affected versions and patch details below.

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

Also known asGHSA-8x6r-g9mw-2r78

Published

Jun 2, 2026

Updated

Oct 28, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Nov 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42342.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs23th percentile — riskier than 23% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

9Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

react-routernpm

74.9Mdownloads / week

@remix-run/server-runtimenpm

1.1Mdownloads / week

Description

React Router is a router for React. In versions 7.0.0 through 7.14.x of react-router and versions 2.10.0 through 2.17.4 of @remix-run/server-runtime, certain crafted requests can consume disproportionate server resources via unbounded path expansion in the __manifest endpoint, resulting in response time degradation and/or service unavailability for end users. This affects React Router Framework Mode applications as well as Remix applications. This does not impact applications using Declarative Mode (<BrowserRouter>) or Data Mode (createBrowserRouter/<RouterProvider>). This is patched in react-router version 7.15.0 and @remix-run/server-runtime version 2.17.5.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`react-router`	≥ 7.0.0&&< 7.15.0	7.15.0`npm install react-router@7.15.0`
📦npm	`@remix-run/server-runtime`	≥ 2.10.0&&< 2.17.5	2.17.5`npm install @remix-run/server-runtime@2.17.5`

Affected Products

2 products · 2 configurations

Application

react-routershopify

≥ 7.0.0 && < 7.15.0

range

Application

remix-run\/server-runtimeshopify

≥ 2.10.0 && < 2.17.5

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for react-router, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update react-router to 7.15.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42342 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

A flaw was found in React Router (Framework Mode) and Remix (@remix-run/server-runtime). Crafted requests to the __manifest endpoint can trigger unbounded path expansion, consuming disproportionate server resources and causing denial of service through response time degradation or complete service unavailability. This…

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. Upgrade to a patched version to fully mitigate the issues (ref: https://github.com/remix-run/react-router/security/advisories/GHSA-8x6r-g9mw-2r78).

Source: Red Hat security advisory for CVE-2026-42342 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat Data Grid 8.6.2	`react-router`	RHSA-2026:41951
Red Hat Migration Toolkit for Applications 8.1	`mta/mta-ui-rhel9:1785169013`	RHSA-2026:50300
Red Hat OpenShift AI 3.4	`rhoai/odh-dashboard-rhel9:1787347991`	RHSA-2026:60520
Red Hat Openshift Data Foundation 4.18	`odf4/cephcsi-rhel9:1786705347`	RHSA-2026:56431
Red Hat Openshift Data Foundation 4.19	`odf4/cephcsi-rhel9:1786701839`	RHSA-2026:56366
Red Hat OpenShift Dev Spaces 3.29	`devspaces/dashboard-rhel9:1784737150`	RHSA-2026:48124
Red Hat Trusted Artifact Signer 1.3	`rhtas/rhtas-console-ui-rhel9:1784105894`	RHSA-2026:42085

Frequently Asked Questions

React Router is a router for React. In versions 7.0.0 through 7.14.x of react-router and versions 2.10.0 through 2.17.4 of @remix-run/server-runtime, certain crafted requests can consume disproportionate server resources via unbounded path expansion in the __manifest endpoint, resulting in response time degradation and/or service unavailability for end users. This affects React Router Framework Mode applications as well as Remix applications. This does not impact applications using Declarative Mode (`<BrowserRouter>`) or Data Mode (`createBrowserRouter/<RouterProvider>`). This is patched in re

O3 Security · Impact-Aware SCA

Is CVE-2026-42342 in your dependencies?

Find it across npm, including transitive dependencies.

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CVSS Score

7.5/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Raw vector

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

CWE Classification

CWE-400Uncontrolled Resource Consumption

Weaponization

No Nuclei template, Metasploit module or public proof-of-concept found.

Timeline

Disclosed

Jun 2, 2026

Last updated

Oct 28, 2026

Identifiers

CVE-2026-42342

GHSA-8x6r-g9mw-2r78

References

Advisorygithub.com · CVE 2026 42342.json Advisorygithub.com · GHSA 8x6r g9mw 2r78 Advisorynvd.nist.gov · CVE 2026 42342 Packagegithub.com · react router

Related vulnerabilities

This CVE is high severity; 3 of 8 other CVEs affecting react-router are rated as high or higher (top: high).

CVE-2026-55685GHSA-qwww-vcr4-c8h2CVE-2026-53666CVE-2026-53667CVE-2026-53668CVE-2026-53669CVE-2026-53663CVE-2026-34077

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 28, 2026

CVE-2026-42342 — react-router

Exploitation Status

No confirmed exploitation observed yet

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Fixing This On Your OS

Frequently Asked Questions

Is CVE-2026-42342 in your dependencies?