GHSA-fv66-9v8q-g76r is a critical-severity (CVSS 10) Deserialization of Untrusted Data vulnerability in react-server-dom-webpack. It is in CISA's Known Exploited Vulnerabilities catalog (added 2025-12-05) and has been used in ransomware campaigns — treat it as actively exploited and patch now. A fix is available for react-server-dom-webpack — see the affected versions and patch details below.
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2025-12-05 — including use in ransomware campaigns. Federal agencies were required to remediate by 2025-12-12.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for GHSA-fv66-9v8q-g76r.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-fv66-9v8q-g76r by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).
Where this sits among everything scored
Of 394,803 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.
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-webpacknpmDescription
Impact
There is an unauthenticated remote code execution vulnerability in React Server Components.
We recommend upgrading immediately.
The vulnerability is present in versions 19.0.0, 19.1.0, 19.1.1, and 19.2.0 of:
Patches
A fix was introduced in versions 19.0.1, 19.1.2, and 19.2.1. 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-webpack | ≥ 19.0.0&&< 19.0.1 | 19.0.1npm install react-server-dom-webpack@19.0.1 |
| 📦npm | react-server-dom-webpack | ≥ 19.1.0&&< 19.1.2 | 19.1.2npm install react-server-dom-webpack@19.1.2 |
| 📦npm | react-server-dom-webpack | ≥ 19.2.0&&< 19.2.1 | 19.2.1npm install react-server-dom-webpack@19.2.1 |
| 📦npm | react-server-dom-turbopack | ≥ 19.0.0&&< 19.0.1 | 19.0.1npm install react-server-dom-turbopack@19.0.1 |
| 📦npm | react-server-dom-turbopack | ≥ 19.1.0&&< 19.1.2 | 19.1.2npm install react-server-dom-turbopack@19.1.2 |
| 📦npm | react-server-dom-turbopack | ≥ 19.2.0&&< 19.2.1 | 19.2.1npm install react-server-dom-turbopack@19.2.1 |
Affected Products
reactfacebooknext.jsvercelResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
React Server 19.2.0 - Remote Code Execution
by danieljavanrad · Apr 9, 2026
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-webpack, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update react-server-dom-webpack to 19.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fv66-9v8q-g76r 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.
How to detect GHSA-fv66-9v8q-g76r
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id ghsa-fv66-9v8q-g76r -u https://target- Template
- React Server Components - Remote Code Execution
- Severity
- critical
- Impact
- Unauthenticated attackers can execute arbitrary code remotely, potentially leading to full system compromise.
- Remediation
- Update to the latest version that fixes the unsafe deserialization issue.
Template by ProjectDiscovery nuclei-templates (DhiyaneshDk, princechaddha, assetnote), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is GHSA-fv66-9v8q-g76r in your dependencies?
Find it across npm, including transitive dependencies.