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React Router SSR XSS in ScrollRestoration

High severity GitHub Reviewed Published Jan 8, 2026 in remix-run/react-router • Updated Jan 8, 2026

Package

npm @remix-run/react (npm)

Affected versions

< 2.17.3

Patched versions

2.17.3
npm react-router (npm)
>= 7.0.0, < 7.12.0
7.12.0

Description

A XSS vulnerability exists in in React Router's <ScrollRestoration> API in Framework Mode when using the getKey/storageKey props during Server-Side Rendering which could allow arbitrary JavaScript execution during SSR if untrusted content is used to generate the keys.

Note

This does not impact applications if developers have disabled server-side rendering in Framework Mode, or if they are using Declarative Mode (<BrowserRouter>) or Data Mode (createBrowserRouter/<RouterProvider>).

References

@brophdawg11 brophdawg11 published to remix-run/react-router Jan 8, 2026
Published to the GitHub Advisory Database Jan 8, 2026
Reviewed Jan 8, 2026
Last updated Jan 8, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality
High
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N

EPSS score

Weaknesses

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Learn more on MITRE.

CVE ID

CVE-2026-21884

GHSA ID

GHSA-8v8x-cx79-35w7

Source code

Credits

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