CVE-2026-112085
HighCVSS 8.2Exploitation Probability (EPSS)
Low risk4th percentile - higher than 4% of all known CVEs
Summary
webpack-dev-server is a development server that provides live reloading for webpack projects. In versions before 5.2.7 and in version 6.0.0, when a proxy entry is configured to forward WebSockets, the server forwards non-HMR WebSocket upgrade requests to the proxy target without validating the Host or Origin headers, so the allowedHosts protection does not apply to those proxied upgrades. A malicious web page visited by a developer can open a cross-origin WebSocket through the dev server and read from and write to the proxied backend, even when the server is bound to loopback.
Risk Assessment
A malicious page can reach the proxied backend through the developer's dev server, potentially leading to unauthorized actions or data exposure. The risk applies to development environments with WebSocket forwarding in proxy entries.
Recommendation
Update webpack-dev-server to version 5.2.7 or 6.1.0 or later. As a workaround, omit WebSocket forwarding from proxy entries that do not need it and scope the proxy to specific paths.
Other vulnerabilities in webpack-dev-server
See all- CVE-2026-114348Medium
webpack-dev-server versions 5.1.0 before 5.2.7 and version 6.0.0 have an unauthenticated open-editor endpoint that validates the Host header with a regular expression meant for browser Origin schemes. A Host value beginning with file: or an extension scheme bypasses hostname and allowedHosts checks, and URL construction throws. In default non-production mode the server returns HTTP 500 with a full stack trace, disclosing filesystem paths, module locations, and source line numbers.
- CVE-2026-14631Medium
A vulnerability in webpack-dev-server versions 5.2.5 and earlier crashes the entire Node.js process when an unauthenticated peer sends a malformed Host header in an HTTP request or a malformed Origin header in a WebSocket upgrade. The malformed value triggers an uncaught exception in the host-validation path, crashing the dev server.
- CVE-2026-14620Medium
A vulnerability in webpack-dev-server versions 5.2.5 and earlier allows an attacker to perform unauthorized actions on the dev server by sending GET requests to internal endpoints. The attack requires no user interaction beyond the developer visiting a malicious website while the dev server is running.
- CVE-2026-9595Medium
A vulnerability in webpack-dev-server allows for the interception of browser cookies and the Origin header when a user-configured proxy has a broad context and ws: true enabled. This leads to bypassing Host/Origin validation and corrupting the HMR socket.
Original NVD description (English source)
webpack-dev-server is a development server that provides live reloading for webpack projects. In versions before 5.2.7 and in version 6.0.0, when a proxy entry is configured to forward WebSockets, the server forwards non-HMR WebSocket upgrade requests to the proxy target without validating the Host or Origin headers, so the allowedHosts protection does not apply to those proxied upgrades. A malicious web page visited by a developer can open a cross-origin WebSocket through the dev server and read from and write to the proxied backend, even when the server is bound to loopback. The issue is fixed in webpack-dev-server 5.2.7 and 6.1.0, where proxied WebSocket upgrades pass the same Host and Origin validation as the HMR WebSocket, and users should upgrade to one of those versions or later. As a workaround, omit WebSocket forwarding from proxy entries that do not need it and scope the proxy to specific paths.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS