CVE-2026-9595webpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies
Updated under an hour ago ()
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It affects webpack-dev-server and 1 other product. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 5.3 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- Weakness (CWE)
- CWE-346, CWE-441
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- openjs
- NVD analysis
- Analyzed
- Record last updated
- Jun 15, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
webpack-dev-server webpack-dev-server webpack_dev_server:webpack_dev_server (from the name) | before 5.2.5; 5.2.5 not affected | CNA record |
webpack.js webpack-dev-server webpack.js:webpack-dev-server | before 5.2.5 | NVD |
References
- https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-mx8g-39q3-5c79mitigation, vendor-advisory
- https://cna.openjsf.org/security-advisories.htmlvendor-advisory
- https://github.com/webpack/webpack-dev-server/pull/4316issue-tracking, patch
- https://github.com/vuejs/vue-cli/commit/72ba7505aff2a8314e82aa5082379a77504a1fcbpatch
- https://github.com/facebook/create-react-app/pull/7444issue-tracking, patch
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.