What is CVE-2026-23870?

CVE-2026-23870 is a high-severity uncontrolled resource consumption vulnerability in react-server-dom-parcel (npm), affecting versions >= 19.0.0, < 19.0.6. It is fixed in 19.0.6, 19.1.7, 19.2.6. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.

How severe is CVE-2026-23870?

CVE-2026-23870 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Which packages are affected by CVE-2026-23870?

react-server-dom-parcel (npm) versions >= 19.0.0, = 19.0.0, = 19.0.0, < 19.0.6.

Is there a fix for CVE-2026-23870?

Yes. CVE-2026-23870 is fixed in 19.0.6, 19.1.7, 19.2.6. Upgrade to this version or later.

Is CVE-2026-23870 exploitable, and should I be worried?

Whether CVE-2026-23870 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2026-23870 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

How do I fix CVE-2026-23870?

Upgrade: react-server-dom-parcel to 19.0.6 or later, react-server-dom-turbopack to 19.0.6 or later, react-server-dom-webpack to 19.0.6 or later, react-server-dom-parcel to 19.1.7 or later, react-server-dom-turbopack to 19.1.7 or later, react-server-dom-webpack to 19.1.7 or later, react-server-dom-parcel to 19.2.6 or later, react-server-dom-turbopack to 19.2.6 or later, react-server-dom-webpack to 19.2.6 or later.

CVE-2026-23870 in react-server-dom-parcel | Intelligent Application Security

Q: How severe is CVE-2026-23870?

CVE-2026-23870 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Q: Which packages are affected by CVE-2026-23870?

react-server-dom-parcel (npm) versions >= 19.0.0, = 19.0.0, = 19.0.0, < 19.0.6.

Q: Is there a fix for CVE-2026-23870?

Yes. CVE-2026-23870 is fixed in 19.0.6, 19.1.7, 19.2.6. Upgrade to this version or later.

Q: Is CVE-2026-23870 exploitable, and should I be worried?

Whether CVE-2026-23870 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2026-23870 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Q: How do I fix CVE-2026-23870?

Upgrade: react-server-dom-parcel to 19.0.6 or later, react-server-dom-turbopack to 19.0.6 or later, react-server-dom-webpack to 19.0.6 or later, react-server-dom-parcel to 19.1.7 or later, react-server-dom-turbopack to 19.1.7 or later, react-server-dom-webpack to 19.1.7 or later, react-server-dom-parcel to 19.2.6 or later, react-server-dom-turbopack to 19.2.6 or later, react-server-dom-webpack to 19.2.6 or later.

Summary

Facebook React has a Denial of Service Vulnerability in React Server Components

Impact

A denial of service vulnerability could be triggered by sending specially crafted HTTP requests to server function endpoints, this could lead to out-of-memory exceptions or excessive CPU usage.

We recommend updating immediately.

The vulnerability exists in versions 19.0.0 through 19.0.5, 19.1.0 through 19.1.6, and 19.2.0 through 19.2.5 of:

react-server-dom-webpack
react-server-dom-parcel
react-server-dom-turbopack

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2026-23870 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (19.0.6, 19.1.7, 19.2.6); upgrading removes the vulnerable code path.

Affected versions

react-server-dom-parcel (>= 19.0.0, < 19.0.6) react-server-dom-turbopack (>= 19.0.0, < 19.0.6) react-server-dom-webpack (>= 19.0.0, < 19.0.6) react-server-dom-parcel (>= 19.1.0, < 19.1.7) react-server-dom-turbopack (>= 19.1.0, < 19.1.7) react-server-dom-webpack (>= 19.1.0, < 19.1.7) react-server-dom-parcel (>= 19.2.0, < 19.2.6) react-server-dom-turbopack (>= 19.2.0, < 19.2.6) react-server-dom-webpack (>= 19.2.0, < 19.2.6)

Security releases

react-server-dom-parcel → 19.0.6 (npm) react-server-dom-turbopack → 19.0.6 (npm) react-server-dom-webpack → 19.0.6 (npm) react-server-dom-parcel → 19.1.7 (npm) react-server-dom-turbopack → 19.1.7 (npm) react-server-dom-webpack → 19.1.7 (npm) react-server-dom-parcel → 19.2.6 (npm) react-server-dom-turbopack → 19.2.6 (npm) react-server-dom-webpack → 19.2.6 (npm)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

See it in your environment

Remediation advice

Fixes were back ported to versions 19.0.6, 19.1.7, and 19.2.6.

If you are using any of the above packages please upgrade to any of the fixed versions immediately.

If your app’s React code does not use a server, your app is not affected by this vulnerability. If your app does not use a framework, bundler, or bundler plugin that supports React Server Components, your app is not affected by this vulnerability.

References
See the blog post for more information and upgrade instructions.

Frequently Asked Questions

What is CVE-2026-23870? CVE-2026-23870 is a high-severity uncontrolled resource consumption vulnerability in react-server-dom-parcel (npm), affecting versions >= 19.0.0, < 19.0.6. It is fixed in 19.0.6, 19.1.7, 19.2.6. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
How severe is CVE-2026-23870? CVE-2026-23870 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Which packages are affected by CVE-2026-23870?
- react-server-dom-parcel (npm) (versions >= 19.0.0, < 19.0.6)
- react-server-dom-turbopack (npm) (versions >= 19.0.0, < 19.0.6)
- react-server-dom-webpack (npm) (versions >= 19.0.0, < 19.0.6)
Is there a fix for CVE-2026-23870? Yes. CVE-2026-23870 is fixed in 19.0.6, 19.1.7, 19.2.6. Upgrade to this version or later.
Is CVE-2026-23870 exploitable, and should I be worried? Whether CVE-2026-23870 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2026-23870 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2026-23870?
- Upgrade react-server-dom-parcel to 19.0.6 or later
- Upgrade react-server-dom-turbopack to 19.0.6 or later
- Upgrade react-server-dom-webpack to 19.0.6 or later
- Upgrade react-server-dom-parcel to 19.1.7 or later
- Upgrade react-server-dom-turbopack to 19.1.7 or later
- Upgrade react-server-dom-webpack to 19.1.7 or later
- Upgrade react-server-dom-parcel to 19.2.6 or later
- Upgrade react-server-dom-turbopack to 19.2.6 or later
- Upgrade react-server-dom-webpack to 19.2.6 or later

Other vulnerabilities in react-server-dom-parcel

CVE-2026-23870 CVE-2026-23869 CVE-2026-23864 CVE-2025-55184 CVE-2025-55183