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HIGH severity

CVE-2026-42211 — react-router

HIGH

CVE-2026-42211 is a high-severity (CVSS 8.1) Deserialization of Untrusted Data vulnerability in react-router. A fix is available for react-router — see the affected versions and patch details below.

React Router's vendored turbo-stream v2 allows arbitrary constructor invocation via TYPE_ERROR deserialization leading to Unauth RCE

Also known asGHSA-49rj-9fvp-4h2h
Published
Jun 2, 2026
Updated
Aug 12, 2026
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Sep 26, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • A successful exploit gives an attacker total control of the affected component, not partial access.
  • 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-2026-42211.

EPSS Exploitation Probability

via FIRST.org ↗
0.6%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs48th percentile — riskier than 48% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2026-42211 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg 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
63.5Mdownloads / week

Description

React Router is a router for React. In versions 7.0.0 through 7.14.1, when using Framework Mode, a combination of steps could potentially allow unauthorized remote code execution (RCE) through external requests. This attack requires the application code to have an existing prototype pollution vulnerability, which can then be leveraged in a 2-step attack where the second step triggers unauthorized RCE on the remote server. This does not impact applications using Declarative Mode (<BrowserRouter>) or Data Mode (createBrowserRouter/<RouterProvider>). This is patched in version 7.14.2.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmreact-router≥ 7.0.0&&< 7.14.27.14.2npm install react-router@7.14.2

Affected Products

1 product · 1 configurations
Application
react-routershopify
≥ 7.0.0 && < 7.14.2
range

Detection & mitigation playbook

Open-source dependency

  1. 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.

  2. Fix

    Update react-router to 7.14.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42211 is resolved across your whole dependency graph.

  3. Workarounds

    Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

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 HatImportant

An Important remote code execution flaw exists in React Router versions 7.0.0 through 7.14.1 when utilized in Framework Mode. This vulnerability requires an existing prototype pollution flaw within the application to enable a two-step attack, leading to unauthorized remote code execution on the server. Red Hat…

Workaround published by Red Hat
To mitigate this vulnerability, ensure that applications using React Router are not configured in Framework Mode. Instead, utilize Declarative Mode (`<BrowserRouter>`) or Data Mode (`createBrowserRouter/<RouterProvider>`), as these modes are not susceptible to this flaw.
Source: Red Hat security advisory for CVE-2026-42211 (CC BY 4.0)
ProductFixed inAdvisory
Red Hat build of Keycloak 26.6rhbk/keycloak-operator-bundle:26.6.7-3RHSA-2026:68277
Red Hat build of Keycloak 26.6.7react-routerRHSA-2026:68278
Red Hat Data Grid 8.6.2react-routerRHSA-2026:41951
Red Hat Hardened Imagesopentelemetry-collector-contrib-main-0.155.0-0.1.hum1RHSA-2026:29770
Red Hat OpenShift AI 3.4rhoai/odh-dashboard-rhel9:1787347991RHSA-2026:60520
Red Hat Trusted Artifact Signer 1.3rhtas/rhtas-console-ui-rhel9:1784105894RHSA-2026:42085

Frequently Asked Questions

React Router is a router for React. In versions 7.0.0 through 7.14.1, when using Framework Mode, a combination of steps could potentially allow unauthorized remote code execution (RCE) through external requests. This attack requires the application code to have an existing prototype pollution vulnerability, which can then be leveraged in a 2-step attack where the second step triggers unauthorized RCE on the remote server. This does not impact applications using Declarative Mode (`<BrowserRouter>`) or Data Mode (`createBrowserRouter/<RouterProvider>`). This is patched in version 7.14.2.
O3 Security · Impact-Aware SCA

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CVE-2026-42211: react-router RCE (High 8.1) | O3 Security