OpenJS webpack-dev-server up to 5.2.6/6.0.x WebSocket Upgrade cross-domain policy

Summaryinfo

A vulnerability identified as problematic has been detected in OpenJS webpack-dev-server up to 5.2.6/6.0.x. The impacted element is an unknown function of the component WebSocket Upgrade. This manipulation causes cross-domain policy. This vulnerability is registered as CVE-2026-112085. Remote exploitation of the attack is possible. No exploit is available. You should upgrade the affected component.

Detailsinfo

A vulnerability has been found in OpenJS webpack-dev-server up to 5.2.6/6.0.x and classified as problematic. Affected by this vulnerability is some unknown functionality of the component WebSocket Upgrade. The manipulation with an unknown input leads to a cross-domain policy vulnerability. The CWE definition for the vulnerability is CWE-942. The product uses a cross-domain policy file that includes domains that should not be trusted. As an impact it is known to affect confidentiality. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-112085 since 10/18/2026. The exploitation appears to be difficult. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available.

Upgrading to version 5.2.7 or 6.1.0 eliminates this vulnerability.

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Productinfo

Vendor

• OpenJS

Name

• webpack-dev-server

Version

• 5.2.0
• 5.2.1
• 5.2.2
• 5.2.3
• 5.2.4
• 5.2.5
• 5.2.6
• 6.0

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