webpack-dev-server vulnerable to cross-origin source code exposure on non-HTTPS origins
cve-program · CVE-2026-6402
Publishedwebpack-dev-server versions up to and including 5.2.3 are vulnerable to cross-origin source code exposure when serving over a non-potentially trustworthy origin such as plain HTTP. The previous fix relied on the Sec-Fetch-Mode and Sec-Fetch-Site request headers, which browsers omit for non-trustworthy origins, allowing a malicious site to load the bundled source as a script and read it across origins. Impact: an attacker controlling a website visited by a developer running webpack-dev-server can recover the application source code when the dev server runs over HTTP at a guessable host and port. Chromium based browsers from Chrome 142 onward are not affected due to local network access restrictions. Upgrade to webpack-dev-server 5.2.4 or later, which sets Cross-Origin-Resource-Policy: same-origin on responses.
Read the publisher's advisoryeuvd · EUVD-2026-29404
Publishedwebpack-dev-server versions up to and including 5.2.3 are vulnerable to cross-origin source code exposure when serving over a non-potentially trustworthy origin such as plain HTTP. The previous fix relied on the Sec-Fetch-Mode and Sec-Fetch-Site request headers, which browsers omit for non-trustworthy origins, allowing a malicious site to load the bundled source as a script and read it across origins. Impact: an attacker controlling a website visited by a developer running webpack-dev-server can recover the application source code when the dev server runs over HTTP at a guessable host and port. Chromium based browsers from Chrome 142 onward are not affected due to local network access restrictions. Upgrade to webpack-dev-server 5.2.4 or later, which sets Cross-Origin-Resource-Policy: same-origin on responses.
Read the publisher's advisorynvd · CVE-2026-6402
Publishedwebpack-dev-server versions up to and including 5.2.3 are vulnerable to cross-origin source code exposure when serving over a non-potentially trustworthy origin such as plain HTTP. The previous fix relied on the Sec-Fetch-Mode and Sec-Fetch-Site request headers, which browsers omit for non-trustworthy origins, allowing a malicious site to load the bundled source as a script and read it across origins. Impact: an attacker controlling a website visited by a developer running webpack-dev-server can recover the application source code when the dev server runs over HTTP at a guessable host and port. Chromium based browsers from Chrome 142 onward are not affected due to local network access restrictions. Upgrade to webpack-dev-server 5.2.4 or later, which sets Cross-Origin-Resource-Policy: same-origin on responses.
Read the publisher's advisoryosv · GHSA-79cf-xcqc-c78w
Published### Impact When webpack-dev-server is running on a non-HTTPS origin (the default), cross-origin requests from malicious websites can load the dev server's JavaScript bundles via `<script>` tags. The fix introduced in v5.2.1 (CVE-2025-30359) relied on `Sec-Fetch-Mode` and `Sec-Fetch-Site` request headers to block these requests, but browsers only send these headers for [potentially trustworthy origins](https://w3c.github.io/webappsec-secure-contexts/#is-origin-trustworthy). Over plain HTTP, the headers are absent and the check is bypassed. An attacker who knows the dev server's host, port, and output path can exfiltrate all module source code by intercepting the webpack runtime's module registration. This does not affect Chrome 142+ (and other Chromium-based browsers) due to [local network access restrictions](https://developer.chrome.com/release-notes/142#local_network_access_restrictions). ### Patches Patched in webpack-dev-server >= 5.2.4 by setting `Cross-Origin-Resource-Policy: same-origin` on responses. ### Workarounds Run the dev server with HTTPS enabled (`--https` or `server.type: 'https'` in config). ### Resources - [GHSA-4v9v-hfq4-rm2v](https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-4v9v-hfq4-rm2v) (CVE-2025-30359) - original vulnerability - [GHSA-9jgg-88mc-972h](https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-9jgg-88mc-972h) (CVE-2025-30360) - prior bypass
Read the publisher's advisoryAffected versions, risk and source history
Exploitation and risk
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cve-program · CVE-2026-6402
Publishedwebpack-dev-server vulnerable to cross-origin source code exposure on non-HTTPS origins
webpack-dev-server versions up to and including 5.2.3 are vulnerable to cross-origin source code exposure when serving over a non-potentially trustworthy origin such as plain HTTP. The previous fix relied on the Sec-Fetch-Mode and Sec-Fetch-Site request headers, which browsers omit for non-trustworthy origins, allowing a malicious site to load the bundled source as a script and read it across origins. Impact: an attacker controlling a website visited by a developer running webpack-dev-server can recover the application source code when the dev server runs over HTTP at a guessable host and port. Chromium based browsers from Chrome 142 onward are not affected due to local network access restrictions. Upgrade to webpack-dev-server 5.2.4 or later, which sets Cross-Origin-Resource-Policy: same-origin on responses.
- Source published
- 12 May 2026 07:45:21 UTC
- Source modified
- 12 May 2026 13:00:06 UTC
- Saved here
- 23 Oct 2026 15:48:27 UTC
- Source terms
- CVE Program Terms of Use
Original source record · Cite this exact observation · Complete original publisher JSON
Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS 3.1 · 5.3 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
euvd · EUVD-2026-29404
Publishedwebpack-dev-server versions up to and including 5.2.3 are vulnerable to cross-origin source code exposure when serving over a non-potentially trustworthy origin such as plain HTTP. The previous fix relied on the Sec-Fetch-Mode and Sec-Fetch…
webpack-dev-server versions up to and including 5.2.3 are vulnerable to cross-origin source code exposure when serving over a non-potentially trustworthy origin such as plain HTTP. The previous fix relied on the Sec-Fetch-Mode and Sec-Fetch-Site request headers, which browsers omit for non-trustworthy origins, allowing a malicious site to load the bundled source as a script and read it across origins. Impact: an attacker controlling a website visited by a developer running webpack-dev-server can recover the application source code when the dev server runs over HTTP at a guessable host and port. Chromium based browsers from Chrome 142 onward are not affected due to local network access restrictions. Upgrade to webpack-dev-server 5.2.4 or later, which sets Cross-Origin-Resource-Policy: same-origin on responses.
Additional publisher context
EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.
Original publisher date fields
datePublished: May 12, 2026, 7:45:21 AM
dateUpdated: May 12, 2026, 1:00:06 PM
2 related source bulletins · separate from aliases
msrc_CVE-2026-6402: webpack-dev-server vulnerable to cross-origin source code exposure on non-HTTPS origins
CVE-2026-6402
openSUSE-SU-2026:10979-1: agama-web-ui-21+360.16caae772-44.1 on GA media
CVE-2026-6402 · CVE-2026-9277
- Source published
- May 12, 2026, 7:45:21 AM (timezone not stated)
- Source modified
- May 12, 2026, 1:00:06 PM (timezone not stated)
- Saved here
- 13 Nov 2026 16:06:35 UTC
- Source terms
- ENISA EUVD · source terms and attribution apply
Original source record · Cite this exact observation · Complete original publisher JSON
Source: euvd · ENISA EUVD · source terms and attribution apply. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
EUVD CVSS 3.1 · 5.3 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
nvd · CVE-2026-6402
Publishedwebpack-dev-server versions up to and including 5.2.3 are vulnerable to cross-origin source code exposure when serving over a non-potentially trustworthy origin such as plain HTTP. The previous fix relied on the Sec-Fetch-Mode and Sec-Fetch…
webpack-dev-server versions up to and including 5.2.3 are vulnerable to cross-origin source code exposure when serving over a non-potentially trustworthy origin such as plain HTTP. The previous fix relied on the Sec-Fetch-Mode and Sec-Fetch-Site request headers, which browsers omit for non-trustworthy origins, allowing a malicious site to load the bundled source as a script and read it across origins. Impact: an attacker controlling a website visited by a developer running webpack-dev-server can recover the application source code when the dev server runs over HTTP at a guessable host and port. Chromium based browsers from Chrome 142 onward are not affected due to local network access restrictions. Upgrade to webpack-dev-server 5.2.4 or later, which sets Cross-Origin-Resource-Policy: same-origin on responses.
Additional publisher context
NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.
Source analysis status: Analyzed
Weakness classifications: CWE-749
Original publisher date fields
published: 2026-05-12T09:16:55.640
lastModified: 2026-11-11T20:10:00.273
1 source CPE criteria · context only
- cpe:2.3:a:webpack.js:webpack-dev-server:*:*:*:*:*:*:*:*
The original JSON retains the logical configuration operators, exclusions and version bounds.
- Source published
- 12 May 2026 09:16:55 UTC
- Source modified
- 11 Nov 2026 20:10:00 UTC
- Saved here
- 12 Nov 2026 22:18:32 UTC
- Source terms
- NIST NVD usage terms; underlying source attribution retained
Original source record · Cite this exact observation · Complete original publisher JSON
Source: nvd · NIST NVD usage terms; underlying source attribution retained. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS 3.1 · ce714d77-add3-4f53-aff5-83d477b104bb · Secondary · 5.3 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
CVSS 3.1 · [email protected] · Primary · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
osv · GHSA-79cf-xcqc-c78w
Publishedwebpack-dev-server vulnerable to cross-origin source code exposure on non-HTTPS origins
### Impact When webpack-dev-server is running on a non-HTTPS origin (the default), cross-origin requests from malicious websites can load the dev server's JavaScript bundles via `<script>` tags. The fix introduced in v5.2.1 (CVE-2025-30359) relied on `Sec-Fetch-Mode` and `Sec-Fetch-Site` request headers to block these requests, but browsers only send these headers for [potentially trustworthy origins](https://w3c.github.io/webappsec-secure-contexts/#is-origin-trustworthy). Over plain HTTP, the headers are absent and the check is bypassed. An attacker who knows the dev server's host, port, and output path can exfiltrate all module source code by intercepting the webpack runtime's module registration. This does not affect Chrome 142+ (and other Chromium-based browsers) due to [local network access restrictions](https://developer.chrome.com/release-notes/142#local_network_access_restrictions). ### Patches Patched in webpack-dev-server >= 5.2.4 by setting `Cross-Origin-Resource-Policy: same-origin` on responses. ### Workarounds Run the dev server with HTTPS enabled (`--https` or `server.type: 'https'` in config). ### Resources - [GHSA-4v9v-hfq4-rm2v](https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-4v9v-hfq4-rm2v) (CVE-2025-30359) - original vulnerability - [GHSA-9jgg-88mc-972h](https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-9jgg-88mc-972h) (CVE-2025-30360) - prior bypass
- Source published
- 18 May 2026 13:31:42 UTC
- Source modified
- 10 Sep 2026 03:50:46 UTC
- Saved here
- 24 Oct 2026 13:17:17 UTC
- Source terms
- GitHub Advisory Database · CC-BY-4.0
Original source record · Cite this exact observation · Complete original publisher JSON
Source: osv · GitHub Advisory Database · CC-BY-4.0. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
Publisher rating · MODERATE