CVE-2026-14631 webpack-dev-server vulnerable to denial of service via a malformed Host or Origin header
An unauthenticated attacker can crash the webpack-dev-server process by sending malformed Host or Origin headers, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-14631?
CVE-2026-14631 is a medium-severity denial of service vulnerability in webpack-dev-server, published on 3 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
webpack-dev-server versions 5.2.5 and earlier terminate the whole Node.js process when an unauthenticated peer sends either a normal HTTP request with a malformed Host header or a WebSocket upgrade to the default /ws endpoint with a malformed Origin header. The malformed value causes an uncaught exception in the host-validation path and crashes the dev server. Impact is limited to availability of the development server, no data disclosure, no code execution. Patches: upgrade to webpack-dev-server 5.2.6. Workarounds: keep the dev server bound to localhost (the default) and do not expose it to untrusted networks.
Which versions are affected by CVE-2026-14631?
2 open source packages ship an affected version, including webpack-dev-server. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
webpack-dev-server npm | All versions | 5.2.6 |
webpack-dev-server npm | All versions | 5.2.6 |
Products include Webpack.js Webpack-Dev-Server.
How do I fix CVE-2026-14631?
Upgrade webpack-dev-server to 5.2.6 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-14631 being exploited?
There is no known exploitation of CVE-2026-14631 in the wild and no public exploit code.
Other vulnerabilities in webpack-dev-server
- CVE-2026-112085 webpack-dev-server vulnerable to cross-origin WebSocket access via proxied upgrades
- CVE-2018-14732 Missing Origin Validation in webpack-dev-server
- CVE-2025-30360 webpack-dev-server users' source code may be stolen when they access a malicious web site with non-Chromium based browser
- CVE-2026-114348 webpack-dev-server vulnerable to information disclosure via Host validation bypass in the open-editor endpoint
- CVE-2026-9595 webpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies
Sources
Also known as CLEANSTART-2026-ZE34863, CLSA-2026-1787823957, CLSA-2026-1787931162, GHSA-m28w-2pqf-7qgj, MINI-496g-v3w4-4j96, MINI-85cq-x37g-jc56 and 5 more.