CVE-2026-23870 — react-server-dom-parcel
HIGHCVE-2026-23870 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in react-server-dom-parcel. 1 public exploit reference exists, so weaponization risk is real. A fix is available for react-server-dom-parcel — see the affected versions and patch details below.
Facebook React has a Denial of Service Vulnerability in React Server Components
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-23870.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-23870 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
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.
react-server-dom-parcelnpmreact-server-dom-turbopacknpmreact-server-dom-webpacknpmDescription
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
Patches
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | react-server-dom-parcel | ≥ 19.0.0&&< 19.0.6 | 19.0.6npm install react-server-dom-parcel@19.0.6 |
| 📦npm | react-server-dom-turbopack | ≥ 19.0.0&&< 19.0.6 | 19.0.6npm install react-server-dom-turbopack@19.0.6 |
| 📦npm | react-server-dom-webpack | ≥ 19.0.0&&< 19.0.6 | 19.0.6npm install react-server-dom-webpack@19.0.6 |
| 📦npm | react-server-dom-parcel | ≥ 19.1.0&&< 19.1.7 | 19.1.7npm install react-server-dom-parcel@19.1.7 |
| 📦npm | react-server-dom-turbopack | ≥ 19.1.0&&< 19.1.7 | 19.1.7npm install react-server-dom-turbopack@19.1.7 |
| 📦npm | react-server-dom-webpack | ≥ 19.1.0&&< 19.1.7 | 19.1.7npm install react-server-dom-webpack@19.1.7 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
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 19.0.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-23870 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-23870 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-23870. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-23870 in your dependencies?
O3 Security finds CVE-2026-23870 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.