CVE-2026-21884Network attack vector

Browser JavaScript execution via unescaped restoration keys

Published Jan 10, 2026 · Updated Jan 10, 2026

Cross-site scripting in React Router Framework Mode allows remote attackers to execute JavaScript in a user's browser via crafted keys. ScrollRestoration places attacker-influenced getKey or storageKey values into an inline script during server-side rendering without neutralizing script-breaking content. Exploitation requires SSR, untrusted content feeding either prop, and user interaction; Declarative Mode and Data Mode are unaffected.

CVSS severity8.2
High
EPSS probability0.54%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in React Router Framework Mode allows remote attackers to execute JavaScript in a user's browser via crafted keys. ScrollRestoration places attacker-influenced getKey or storageKey values into an inline script during server-side rendering without neutralizing script-breaking content. Exploitation requires SSR, untrusted content feeding either prop, and user interaction; Declarative Mode and Data Mode are unaffected.

The record

CVE
CVE-2026-21884
Published
Jan 10, 2026
Updated
Jan 10, 2026
Vendor
Shopify
Product
React Router
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=react-router >= 7.0.0, < 7.12.0
  2. Affected versionversion=@remix-run/react < 2.17.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Shopify · React Routerversion=react-router >= 7.0.0, < 7.12.0; version=@remix-run/react < 2.17.3

Published CVSS scores

8.2GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007Command and Scripting Interpreter: JavaScript

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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