CVE-2025-30359: webpack-dev-server — Exploit & Fix

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.

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CVSS v3.1 Score

5.3

MEDIUM

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

Weakness Type (CWE)

CWE-749 CWE-749

Affected Products

Vendor	Product	Versions
webpack.js	webpack-dev-server	< 5.2.1

References

Advisories & Patches

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

Exploits

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

Frequently Asked Questions

What is CVE-2025-30359? +

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. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2025-30359? +

CVE-2025-30359 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-30359? +

CVE-2025-30359 affects products from webpack.js, specifically: webpack-dev-server. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-30359? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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