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CVE-2026-112085

webpack-dev-server vulnerable to cross-origin WebSocket access via proxied upgrades

HIGH
8.2
CVSS Score
Published: October 22, 2026 at 09:31 AM UTC
Updated: October 22, 2026 at 03:25 PM UTC
1 product affected across 1 vendorJs Webpack Dev Server

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Severity
HIGH8.2
Exploit prediction
EPSS 0.1%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Js Webpack Dev Server· Webpack Dev Server
90%
6.0.0
Vendor states this is fixed in 5.2.7 (unaffected)
Vendor states this is fixed in 6.1.0 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (2)

Source: cverecord
https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-cfqc-fj3v-j925
Source: cverecord
https://cna.openjsf.org/security-advisories.html

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

8.2HIGHopenjs
Vector?

Quick Info

StatusUNDERGOING ANALYSIS
CWE
CWE-346CWE-1385

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