CVE-2026-114348 in webpack-dev-server
Summary
by MITRE • 10/22/2026
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.
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Analysis
by VulDB Data Team • 10/22/2026
The vulnerability identified in webpack-dev-server affects development environments where the server operates with live reloading capabilities enabled. Specifically, this issue is present in version ranges from 5.1.0 up to but not including 5.2.7, as well as in version 6.0.0 of the software. The core technical flaw resides within the unauthenticated open-editor endpoint, which is designed to facilitate code editing by opening files directly in an editor via a browser interface. This endpoint relies on validating the Host header sent by clients to ensure that requests originate from allowed sources. However, the validation logic employs a regular expression intended for parsing browser Origin schemes rather than standard HTTP Host headers. Consequently, when a client sends a request with a malformed Host value beginning with file: or utilizing an extension scheme, the regex fails to properly parse the hostname component. This failure causes the subsequent checks against allowedHosts to be short-circuited and bypassed entirely, allowing unauthorized access patterns that would normally be rejected by strict host validation mechanisms.
The operational impact of this vulnerability is primarily informational disclosure rather than service disruption or remote code execution. When a network peer capable of reaching the development server sends such a malformed Host header, it triggers an exception within the endpoint's URL construction logic. In default non-production modes, which are commonly used during active software development, webpack-dev-server responds to these errors by returning an HTTP 500 Internal Server Error response that includes the full stack trace of the thrown exception. This detailed error output inadvertently discloses sensitive internal information about the server environment. Specifically, it reveals absolute filesystem paths where project files and node modules are located, as well as specific source line numbers within the application codebase. While this exposure does not result in a denial of service since the server continues to operate normally after processing the request, it provides attackers with valuable reconnaissance data that can aid in further exploitation attempts or social engineering attacks by confirming internal directory structures and technology stacks.
From a classification perspective, this vulnerability aligns with CWE-209: Generation of Error Message Containing Sensitive Information, as the primary risk stems from the leakage of stack traces containing system-specific details. It also relates to CWE-749: Exposed Dangerous Method or Function, given that the open-editor endpoint is an administrative feature exposed without sufficient authentication in default configurations. In terms of adversary tactics, this behavior supports reconnaissance activities categorized under ATT&CK technique T1083: File and Directory Discovery, as the disclosed paths allow for mapping the target environment's structure. The vulnerability does not facilitate direct system compromise but serves as a stepping stone for deeper investigation into the development infrastructure.
To mitigate this risk, organizations must upgrade webpack-dev-server to version 5.2.7 or later, which includes fixes that properly validate Host headers regardless of scheme prefixes. Alternatively, upgrading to version 6.1.0 and above resolves the issue in newer release lines. For environments where immediate upgrades are not feasible, it is critical to ensure that development servers are never exposed directly to untrusted networks without proper access controls or reverse proxy configurations that strip or normalize Host headers before they reach the application layer. Additionally, developers should configure webpack-dev-server to run in production mode during any phase of testing that involves external network exposure, as this typically suppresses verbose error messages and stack traces, thereby reducing the information leakage potential even if other vulnerabilities exist.