webpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies
cve-program · CVE-2026-9595
PublishedImpact: When a user-configured proxy on webpack-dev-server has a broad context (e.g. /) and ws: true, it also intercepts the dev server's own HMR WebSocket and forwards it to the proxy target. This leaks the browser's cookies and Origin header to the backend, bypasses the dev server's Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket). Patches: Fixed in [email protected]. Workarounds: Scope user-defined proxy context to specific paths instead of /, or omit ws: true from the proxy entry when WebSocket forwarding is not required.
Read the publisher's advisoryeuvd · EUVD-2026-36729
PublishedImpact: When a user-configured proxy on webpack-dev-server has a broad context (e.g. /) and ws: true, it also intercepts the dev server's own HMR WebSocket and forwards it to the proxy target. This leaks the browser's cookies and Origin header to the backend, bypasses the dev server's Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket). Patches: Fixed in [email protected]. Workarounds: Scope user-defined proxy context to specific paths instead of /, or omit ws: true from the proxy entry when WebSocket forwarding is not required.
Read the publisher's advisorynvd · CVE-2026-9595
PublishedImpact: When a user-configured proxy on webpack-dev-server has a broad context (e.g. /) and ws: true, it also intercepts the dev server's own HMR WebSocket and forwards it to the proxy target. This leaks the browser's cookies and Origin header to the backend, bypasses the dev server's Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket). Patches: Fixed in [email protected]. Workarounds: Scope user-defined proxy context to specific paths instead of /, or omit ws: true from the proxy entry when WebSocket forwarding is not required.
Read the publisher's advisoryosv · GHSA-mx8g-39q3-5c79
Published### Impact When a user-configured proxy on `webpack-dev-server` has a broad context (e.g. `/`) and `ws: true`, it also intercepts the dev server's own HMR WebSocket and forwards it to the proxy target. This leaks the browser's cookies and `Origin` header to the backend, bypasses the dev server's Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket). ### Patches Fixed in `webpack-dev-server` 5.2.5. ### Workarounds Scope user-defined proxy `context` to specific paths instead of `/`, or omit `ws: true` from the proxy entry when WebSocket forwarding is not required.
Read the publisher's advisoryAffected versions, risk and source history
Exploitation and risk
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cve-program · CVE-2026-9595
Publishedwebpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies
Impact: When a user-configured proxy on webpack-dev-server has a broad context (e.g. /) and ws: true, it also intercepts the dev server's own HMR WebSocket and forwards it to the proxy target. This leaks the browser's cookies and Origin header to the backend, bypasses the dev server's Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket). Patches: Fixed in [email protected]. Workarounds: Scope user-defined proxy context to specific paths instead of /, or omit ws: true from the proxy entry when WebSocket forwarding is not required.
- Source published
- 15 Jun 2026 15:00:21 UTC
- Source modified
- 15 Jun 2026 16:08:35 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:L/PR:N/UI:N/S:U/C:N/I:N/A:L
euvd · EUVD-2026-36729
PublishedImpact: When a user-configured proxy on webpack-dev-server has a broad context (e.g. /) and ws: true, it also intercepts the dev server's own HMR WebSocket and forwards it to the proxy target. This leaks the browser's cookies and Origin hea…
Impact: When a user-configured proxy on webpack-dev-server has a broad context (e.g. /) and ws: true, it also intercepts the dev server's own HMR WebSocket and forwards it to the proxy target. This leaks the browser's cookies and Origin header to the backend, bypasses the dev server's Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket). Patches: Fixed in [email protected]. Workarounds: Scope user-defined proxy context to specific paths instead of /, or omit ws: true from the proxy entry when WebSocket forwarding is not required.
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: Jun 15, 2026, 3:00:21 PM
dateUpdated: Jun 15, 2026, 4:08:35 PM
16 related source bulletins · separate from aliases
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RHSA-2026:57590: Red Hat Security Advisory: rh-podman-desktop security, bug fix, and enhancement update
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RHSA-2026:41951: Red Hat Security Advisory: Red Hat Data Grid 8.6.2 security update
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RHSA-2026:41928: Red Hat Security Advisory: Red Hat Migration Toolkit for Containers
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RHSA-2026:34794: Red Hat Security Advisory: OpenShift Container Platform 4.22.4 bug fix and security update
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RHSA-2026:51038: Red Hat Security Advisory: OpenShift Container Platform 4.22.9 bug fix and security update
CVE-2026-9595 · CVE-2026-27136 · CVE-2026-39828 · CVE-2026-39835 · CVE-2026-43003 · CVE-2026-44918 · CVE-2026-46597 · CVE-2026-48801 · CVE-2026-49332
RHSA-2026:59153: Red Hat Security Advisory: Red Hat Ansible Automation Platform 2.7 Container Release Update
CVE-2026-9595 · CVE-2026-12143 · CVE-2026-15307 · CVE-2026-27459 · CVE-2026-39363 · CVE-2026-44244 · CVE-2026-44545 · CVE-2026-44705 · CVE-2026-46625 · CVE-2026-59886 · CVE-2026-69243 · CVE-2026-69244 · CVE-2026-71364 · CVE-2026-71365 · CVE-2026-71366
RHSA-2026:37186: Red Hat Security Advisory: OpenShift Container Platform 4.21.24 bug fix and security update
CVE-2026-4800 · CVE-2026-6322 · CVE-2026-9595 · CVE-2026-13676 · CVE-2026-44293
- Source published
- Jun 15, 2026, 3:00:21 PM (timezone not stated)
- Source modified
- Jun 15, 2026, 4:08:35 PM (timezone not stated)
- Saved here
- 13 Nov 2026 18:06:53 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:L/PR:N/UI:N/S:U/C:N/I:N/A:L
nvd · CVE-2026-9595
PublishedImpact: When a user-configured proxy on webpack-dev-server has a broad context (e.g. /) and ws: true, it also intercepts the dev server's own HMR WebSocket and forwards it to the proxy target. This leaks the browser's cookies and Origin hea…
Impact: When a user-configured proxy on webpack-dev-server has a broad context (e.g. /) and ws: true, it also intercepts the dev server's own HMR WebSocket and forwards it to the proxy target. This leaks the browser's cookies and Origin header to the backend, bypasses the dev server's Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket). Patches: Fixed in [email protected]. Workarounds: Scope user-defined proxy context to specific paths instead of /, or omit ws: true from the proxy entry when WebSocket forwarding is not required.
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-346 · CWE-441
Original publisher date fields
published: 2026-06-15T16:16:35.227
lastModified: 2026-06-17T11:05:31.643
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
- 15 Jun 2026 16:16:35 UTC
- Source modified
- 17 Jun 2026 11:05:31 UTC
- Saved here
- 25 Oct 2026 16:19:28 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:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CVSS 3.1 · [email protected] · Primary · 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
osv · GHSA-mx8g-39q3-5c79
Publishedwebpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies
### Impact When a user-configured proxy on `webpack-dev-server` has a broad context (e.g. `/`) and `ws: true`, it also intercepts the dev server's own HMR WebSocket and forwards it to the proxy target. This leaks the browser's cookies and `Origin` header to the backend, bypasses the dev server's Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket). ### Patches Fixed in `webpack-dev-server` 5.2.5. ### Workarounds Scope user-defined proxy `context` to specific paths instead of `/`, or omit `ws: true` from the proxy entry when WebSocket forwarding is not required.
- Source published
- 17 Jun 2026 18:13:31 UTC
- Source modified
- 10 Sep 2026 03:51:09 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:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Publisher rating · MODERATE