Bug 2558806 (CVE-2026-114348)

Summary: CVE-2026-114348 webpack-dev-server: webpack-dev-server: Information disclosure via malformed Host header
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in webpack-dev-server. An unauthenticated remote attacker can exploit improper Host header validation in the open-editor endpoint to obtain sensitive technical information. By sending a request with a specially crafted Host header, the attacker triggers an internal server error that returns a full error stack trace. This exposes environment details, including local file system paths, module locations, and internal source code references.
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Description OSIDB Bzimport 2026-10-22 09:53:13 UTC 
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.