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CVE Record

CVE-2026-21884: React Router SSR XSS in ScrollRestoration

React Router is a router for React. In @remix-run/react version prior to 2.17.3. and react-router 7.0.0 through 7.11.0, 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. There is no impact if server-side rendering in Framework Mode is disabled, or if Declarative Mode (<BrowserRouter>) or Data Mode (createBrowserRouter/<RouterProvider>) is being used. This issue has been patched in @remix-run/react version 2.17.3 and react-router version 7.12.0.

HighCVSS 8.2Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Some React Router server-rendered applications can accidentally place attacker-controlled data into page scripts through ScrollRestoration keys. If exploited, a victim who visits an affected page could run malicious JavaScript in their browser. The issue is limited to specific Framework Mode SSR use, not all React Router applications.

Executive priority

Prioritize remediation for internet-facing React Router or Remix applications that use server-side rendering. The vulnerability is high severity, but exposure is conditional. Teams should quickly confirm whether the affected rendering mode and ScrollRestoration props are present before treating it as broadly exploitable.

Technical view

CVE-2026-21884 is a CWE-79 XSS in React Router's <ScrollRestoration> API when Framework Mode SSR uses getKey or storageKey values derived from untrusted content. Affected versions are @remix-run/react before 2.17.3 and react-router 7.0.0 through 7.11.0. Patched versions are 2.17.3 and 7.12.0.

Likely exposure

Exposure is likely in React or Remix applications using the affected package versions, Framework Mode with server-side rendering, and ScrollRestoration getKey or storageKey props influenced by untrusted content. Declarative Mode, Data Mode, and Framework Mode without SSR are stated as not impacted.

Exploitation context

The CVSS vector is network-accessible with low attack complexity, no privileges required, and user interaction required. The provided sources do not identify active exploitation, and the CVE is not marked KEV. Treat exploit status as unconfirmed unless later vendor or KEV evidence appears.

Researcher notes

Key triage questions are package version, rendering mode, and whether untrusted content can influence getKey or storageKey. The public bundle gives affected ranges and patched versions but does not provide exploit details. Avoid assuming impact for BrowserRouter, createBrowserRouter, RouterProvider, or Framework Mode without SSR.

Mitigation direction

  • Upgrade @remix-run/react to 2.17.3 or later.
  • Upgrade react-router to 7.12.0 or later.
  • Review ScrollRestoration getKey and storageKey generation for untrusted input.
  • If upgrade is delayed, avoid affected Framework Mode SSR usage where feasible.
  • Check React Router and Red Hat guidance for package-specific fixes.

Validation and detection

  • Inventory @remix-run/react and react-router versions in application manifests and lockfiles.
  • Confirm whether the application uses Framework Mode with server-side rendering.
  • Search for ScrollRestoration usage with getKey or storageKey props.
  • Verify deployed builds contain patched dependency versions.
  • Monitor vendor advisories and CISA KEV for exploitation status changes.
Prepared
Confidence
high
Sources
9

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · medium confidence lookup

CWE-79: User-session and phishing behavior lookup

Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-21884 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.2 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
9Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: total

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.2CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N2.84.7GitHub_M
8.2CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N2.84.7redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

8.2High
CVSS 3.1 vector shape for CVE-2026-21884Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPreact-router: @remix-run/react: React Router SSR XSS in ScrollRestoration
other:Red Hat severity ratingcvssV3_1
  • 2026-01-10T04:01:46.246Z: Reported to Red Hat.
  • 2026-01-10T02:41:44.944Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
remix-runreact-router@remix-run/react < 2.17.3, react-router >= 7.0.0, < 7.12.0Listed
Weakness

CWE details

CWE-79

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.