webpack-dev-server users' source code may be stolen when they access a malicious web site with non-Chromium based browser

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

EPSS

• CVE-2025-30360: 0.36% estimated exploitation activity in the next 30 days; percentile 29.52 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Source code may be stolen when you access a malicious web site with non-Chromium based browser. Details The Origin header is checked to prevent Cross-site WebSocket hijacking from happening which was reported by CVE-2018-14732. But webpack-dev-server always allows IP address Origin headers. https://github.com/webpack/webpack-dev-server/blob/55220a800ba4e30dbde2d98785ecf4c80b32f711/lib/Server.js#L3113-L3127 This allows websites that are served on IP addresses to connect WebSocket. By using the same method described in the article linked from CVE-2018-14732, the attacker get the source code. related commit: https://github.com/webpack/webpack-dev-server/commit/72efaab83381a0e1c4914adf401cbd210b7de7eb (note that checkHost function was only used for Host header to prevent DNS rebinding attacks so this change itself is fine. This vulnerability does not affect Chrome 94+ (and other Chromium based browsers) users due to the non-HTTPS private access blocking feature. PoC 1. Download…

Published by the source

4 Jun 2025, 21:09 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:38 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-9jgg-88mc-972h

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-9jgg-88mc-972h

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# Patch Next advisory brief: CVE-2025-30360

Advisory: webpack-dev-server users' source code may be stolen when they access a malicious web site with non-Chromium based browser
IDs: CVE-2025-30360, GHSA-9jgg-88mc-972h
Record: https://patchnext.com/advisories/cve-2025-30360 (revision 2, source checked 26 Oct 2026, 12:38 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: webpack-dev-server 5.2.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm webpack-dev-server: affected <= 5.2.0; fixed in 5.2.1

## Suggested inspection (read-only)
- `npm ls webpack-dev-server --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on webpack-dev-server.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-9jgg-88mc-972h (OSV record GHSA-9jgg-88mc-972h lists affected ranges: npm webpack-dev-server >=0 <5.2.1 (fixed))
- Verified: https://github.com/advisories/GHSA-9jgg-88mc-972h (GitHub-reviewed advisory GHSA-9jgg-88mc-972h lists affected ranges: npm webpack-dev-server >=0 <=5.2.0)

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