How severe is CVE-2026-126187?

No CVSS score has been assigned to CVE-2026-126187 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-126187?

CVE-2026-126187 affects the following packages: react-server-dom-parcel (npm), react-server-dom-parcel (npm), react-server-dom-parcel (npm), react-server-dom-parcel (npm), react-server-dom-turbopack (npm), react-server-dom-turbopack (npm), react-server-dom-turbopack (npm), react-server-dom-turbopack (npm), and 4 more. Ecosystems affected: npm.

How do I fix CVE-2026-126187?

Update react-server-dom-parcel to 19.0.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-126187 is resolved across your whole dependency graph.

How do I detect CVE-2026-126187 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for react-server-dom-parcel, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-126187 if there is no patch (or I can't update yet)?

Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Is CVE-2026-126187 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-126187 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What type of vulnerability is CVE-2026-126187?

CVE-2026-126187 is classified as Deserialization of Untrusted Data (CWE-502). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-126187 published, and has it been updated?

CVE-2026-126187 was published on November 10, 2026 and was last updated on November 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

CVE-2026-126187 — react-server-dom-parcel

Fix: react/react#37842

CVE-2026-126187 is a Deserialization of Untrusted Data vulnerability in react-server-dom-parcel. A fix is available for react-server-dom-parcel — see the affected versions and patch details below.

React: Unauthenticated Remote Code Execution in React Server Components

Published

Nov 10, 2026

Updated

Nov 10, 2026

Affected

12 pkgs

Patched

12 / 12

Exploits

None indexed

Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Real-World Exposure

12 pkgs affected

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.

4other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

react-server-dom-parcelnpm

25Kdownloads / week

Description

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.

Affected Packages

12 total 12 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`react-server-dom-parcel`	≥ 19.0.0&&< 19.0.9	19.0.9`npm install react-server-dom-parcel@19.0.9`
📦npm	`react-server-dom-parcel`	≥ 19.1.0&&< 19.1.10	19.1.10`npm install react-server-dom-parcel@19.1.10`
📦npm	`react-server-dom-parcel`	≥ 19.2.0&&< 19.2.9	19.2.9`npm install react-server-dom-parcel@19.2.9`
📦npm	`react-server-dom-parcel`	≥ 19.3.0&&< 19.3.1	19.3.1`npm install react-server-dom-parcel@19.3.1`
📦npm	`react-server-dom-turbopack`	≥ 19.0.0&&< 19.0.9	19.0.9`npm install react-server-dom-turbopack@19.0.9`
📦npm	`react-server-dom-turbopack`	≥ 19.1.0&&< 19.1.10	19.1.10`npm install react-server-dom-turbopack@19.1.10`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for react-server-dom-parcel, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update react-server-dom-parcel to 19.0.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-126187 is resolved across your whole dependency graph.
Workarounds
Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Frequently Asked Questions

### 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

O3 Security · Impact-Aware SCA

Is CVE-2026-126187 in your dependencies?

Find it across npm, including transitive dependencies.

Scan my dependencies How O3 SCA works