Missing Origin Validation in webpack-dev-serverGHSA-cf66-xwfp-gvc4
HIGHFix: webpack/webpack-dev-server@f18e5adGHSA-cf66-xwfp-gvc4 is a high-severity (CVSS 7.5) Improper Input Validation vulnerability in webpack-dev-server. 2 public exploit references exist, so weaponization risk is real. A fix is available for webpack-dev-server — see the affected versions and patch details below.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-cf66-xwfp-gvc4 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% 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.
webpack-dev-servernpmDescription
Versions of webpack-dev-server before 3.1.10 are missing origin validation on the websocket server. This vulnerability allows a remote attacker to steal a developer's source code because the origin of requests to the websocket server that is used for Hot Module Replacement (HMR) are not validated.
Recommendation
For webpack-dev-server update to version 3.1.11 or later.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | webpack-dev-server | all versions | 3.1.11npm install webpack-dev-server@3.1.11 |
Affected Products
webpack-dev-serverwebpack.jsResearch 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 webpack-dev-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update webpack-dev-server to 3.1.11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-cf66-xwfp-gvc4 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.
Frequently Asked Questions
Is GHSA-cf66-xwfp-gvc4 in your dependencies?
Find it across npm, including transitive dependencies.