CVE-2026-33244 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in react-router. A fix is available for react-router — see the affected versions and patch details below.
React Router has stored XSS via unescaped Location header in prerendered redirect HTML
Exploitation Status
No confirmed exploitation observed yet
- 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-2026-33244.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-33244 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 390,400 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
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.
react-routernpmDescription
React Router is a router for React. In versions 7.5.1 through 7.13.1, when using Framework Mode with pre-rendering enabled, improper neutralization of the HTTP Location header value can permit Cross-Site Scripting (XSS) in the statically generated HTML files if the redirect location comes from an untrusted source. This does not impact applications using Declarative Mode (<BrowserRouter>) or Data Mode (createBrowserRouter/<RouterProvider>). This is patched in version 7.13.2.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | react-router | ≥ 7.5.1&&< 7.13.2 | 7.13.2npm install react-router@7.13.2 |
Affected Products
react-routershopifyDetection & mitigation playbook
Open-source dependencyDetect
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 7.13.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33244 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
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.
This Moderate flaw in `react-router` affects applications using Framework Mode with pre-rendering enabled, allowing cross-site scripting (XSS). An untrusted HTTP `Location` header can inject malicious scripts into statically generated HTML. Red Hat products are only vulnerable if deployed with this specific…
To mitigate this issue, Red Hat customers should ensure that applications utilizing React Router avoid Framework Mode with pre-rendering enabled, particularly when handling redirect locations from untrusted sources. If this mode is essential, strict validation and sanitization of all input used in redirect URLs are required. Applications configured with Declarative Mode (`<BrowserRouter>`) or Data Mode (`createBrowserRouter/<RouterProvider>`) are not susceptible to this flaw.Source: Red Hat security advisory for CVE-2026-33244 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2026-33244 in your dependencies?
Find it across npm, including transitive dependencies.