---
id: "CVE-2026-114348"
kind: "vulnerability"
aliases: ["CVE-2026-114348"]
title: "webpack-dev-server: Host header check leaks stack traces and file paths"
severity: "medium"
cvss: 5.3
epss: 0.00305
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["frontend", "javascript", "node", "package", "webpack", "webpack-dev-server"]
not_affected_if: ["localhost-only-dev", "production-build", "version-outside-range"]
published_at: "2026-10-22T10:17:08+00:00"
first_seen_at: "2026-10-23T21:57:30+00:00"
updated_at: "2026-10-25T04:20:23+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-114348", "first_seen_at": "2026-10-23T21:57:30+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-114348", "first_seen_at": "2026-10-24T07:15:51+00:00"}]
---

# webpack-dev-server: Host header check leaks stack traces and file paths

webpack-dev-server's open-editor endpoint validates the Host header with a flawed regex, so a malformed Host value gets past the allowed-hosts check and triggers an exception. In non-production mode the 500 response includes the full stack trace, exposing absolute filesystem paths, module locations and source line numbers.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `npm ls webpack-dev-server` to find the installed version; affected versions are 5.1.0 through 5.2.6 and 6.0.0.
- Check whether the dev server is reachable from untrusted networks, for example bound to `0.0.0.0` or exposed through a tunnel.

## Fix

- Upgrade webpack-dev-server to `5.2.7` (5.x line) or `6.1.0` (6.x line) or later.
- Keep the dev server bound to localhost or behind a trusted network until upgraded.

## Timeline

- 2026-10-23T21:57:30+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-114348
- 2026-10-24T07:15:51+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-114348

## From the sources

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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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_