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Critical, CVSS 9.5amended

React: Unauthenticated Remote Code Execution in React Server Components

CVE-2026-126187GHSA-xqc2-xf4c-x3h3

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (react-server-dom-turbopack 19.3.1, 19.2.9, 19.1.10, 19.0.9; react-server-dom-parcel 19.3.1, 19.2.9, 19.1.10, 19.0.9; react-server-dom-webpack 19.3.1, 19.2.9, 19.1.10, 19.0.9), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • npm react-server-dom-turbopack

    Affected
    >= 19.0.0, < 19.0.9>= 19.1.0, < 19.1.10>= 19.2.0, < 19.2.9>= 19.3.0, < 19.3.1
    Fixed in
    19.2.9, 19.0.9, 19.1.10, 19.3.1

  • npm react-server-dom-parcel

    Affected
    >= 19.0.0, < 19.0.9>= 19.1.0, < 19.1.10>= 19.2.0, < 19.2.9>= 19.3.0, < 19.3.1
    Fixed in
    19.2.9, 19.0.9, 19.1.10, 19.3.1

  • npm react-server-dom-webpack

    Affected
    >= 19.0.0, < 19.0.9>= 19.1.0, < 19.1.10>= 19.2.0, < 19.2.9>= 19.3.0, < 19.3.1
    Fixed in
    19.2.9, 19.0.9, 19.1.10, 19.3.1

Sources

  • GitHub Advisory Database and maintainer security advisories on GitHub

    GitHub-reviewed advisory GHSA-xqc2-xf4c-x3h3 lists affected ranges: npm react-server-dom-parcel >=19.0.0 =19.1.0 =19.2.0 =19.3.0 =19.0.0 =19.1.0 =19.2.0 =19.3.0 =19.0.0 =19.1.0 =19.2.0 =19.3.0 <19.3.1

    VerifiedObserved Structured GitHub Advisory Database record (type=reviewed) from the GitHub REST API.

  • Open Source Vulnerabilities (OSV.dev), including the GitHub Advisory Database

    OSV record GHSA-xqc2-xf4c-x3h3 lists affected ranges: npm react-server-dom-parcel >=19.0.0 =19.1.0 =19.2.0 =19.3.0 =19.0.0 =19.1.0 =19.2.0 =19.3.0 =19.0.0 =19.1.0 =19.2.0 =19.3.0 <19.3.1 (fixed)

    VerifiedObserved Structured OSV record; GitHub-reviewed advisory.

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
9.5 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:N · score source
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

Impact Crafted payloads targeting frameworks supporting React Server Components can lead to remote code execution. This only affects extremely rare cases where responses transport multiple typed arrays and an attacker-controlled value. Updating immediately is recommended. The vulnerability exists in versions 19.0.0 through 19.0.8, 19.1.0 through 19.1.9, 19.2.0 through 19.2.8 and 19.3.0 of: - react-server-dom-webpack - react-server-dom-parcel - react-server-dom-turbopack

Patches Fixes were back ported to versions 19.0.09, 19.1.10, 19.2.9, and 19.3.1. If applications are using any of the above packages please upgrade to any of the fixed versions immediately. If an app’s React code does not use a server, the app is not affected by this vulnerability. If an app does not use a framework, bundler, or bundler plugin that supports React Server Components, the app is not affected by this vulnerability.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from osv record GHSA-xqc2-xf4c-x3h3

  2. Revision 1 · created ·

    Published from ghsa record GHSA-xqc2-xf4c-x3h3

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-126187

Advisory: React: Unauthenticated Remote Code Execution in React Server Components
IDs: CVE-2026-126187, GHSA-xqc2-xf4c-x3h3
Record: https://patchnext.com/advisories/cve-2026-126187 (revision 2, source checked 11 Nov 2026, 06:00 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: react-server-dom-turbopack 19.3.1, 19.2.9, 19.1.10, 19.0.9; react-server-dom-parcel 19.3.1, 19.2.9, 19.1.10, 19.0.9; react-server-dom-webpack 19.3.1, 19.2.9, 19.1.10, 19.0.9. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm react-server-dom-turbopack: affected >= 19.0.0, < 19.0.9; >= 19.1.0, < 19.1.10; >= 19.2.0, < 19.2.9; >= 19.3.0, < 19.3.1; fixed in 19.2.9, 19.0.9, 19.1.10, 19.3.1
- npm react-server-dom-parcel: affected >= 19.0.0, < 19.0.9; >= 19.1.0, < 19.1.10; >= 19.2.0, < 19.2.9; >= 19.3.0, < 19.3.1; fixed in 19.2.9, 19.0.9, 19.1.10, 19.3.1
- npm react-server-dom-webpack: affected >= 19.0.0, < 19.0.9; >= 19.1.0, < 19.1.10; >= 19.2.0, < 19.2.9; >= 19.3.0, < 19.3.1; fixed in 19.2.9, 19.0.9, 19.1.10, 19.3.1

## Suggested inspection (read-only)
- `npm ls react-server-dom-turbopack --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls react-server-dom-parcel --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls react-server-dom-webpack --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on react-server-dom-turbopack, react-server-dom-parcel, react-server-dom-webpack.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-xqc2-xf4c-x3h3 (GitHub-reviewed advisory GHSA-xqc2-xf4c-x3h3 lists affected ranges: npm react-server-dom-parcel >=19.0.0 =19.1.0 =19.2.0 =19.3.0 =19.0.0 =19.1.0 =19.2.0 =19.3.0 =19.0.0 =19.1.0 =19.2.0 =19.3.0 <19.3.1)
- Verified: https://osv.dev/vulnerability/GHSA-xqc2-xf4c-x3h3 (OSV record GHSA-xqc2-xf4c-x3h3 lists affected ranges: npm react-server-dom-parcel >=19.0.0 =19.1.0 =19.2.0 =19.3.0 =19.0.0 =19.1.0 =19.2.0 =19.3.0 =19.0.0 =19.1.0 =19.2.0 =19.3.0 <19.3.1 (fixed))

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