Description
webpack-dev-server is a development server that provides live reloading for webpack projects. In versions from 5.1.0 before 5.2.7 and in version 6.0.0, the unauthenticated open-editor endpoint validates the Host header with a regular expression meant for browser Origin schemes, so a Host value beginning with file: or with an extension scheme short-circuits the hostname and allowedHosts checks. A network peer that can reach the dev server can send a request with a malformed Host that passes validation and then causes the endpoint's URL construction to throw, and in the default non-production mode the server returns an HTTP 500 body containing the full exception stack trace, which discloses absolute filesystem paths, installed module locations, and internal source line numbers. The server keeps running, so there is no denial of service. The issue is fixed in webpack-dev-server 5.2.7 and 6.1.0, and users should upgrade to one of those versions or later.
Affected products
webpack.js: webpack-dev-server
References2
- cna.openjsf.org/security-advisories.html Vendor Advisory
- github.com/webpack/webpack-dev-server/security/advisories/GHSA-… Vendor Advisory
Metrics
- CVSS 3.1
-
5.3
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - EPSS — exploit probability
- 0% percentile: 23 · as of 8 November 2026
- CWE
- CWE-209CWE-1289
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.