{"cve":"CVE-2026-9595","nvd":{"published":"2026-06-15T16:16:35.227","modified":"2026-06-17T11:05:31.643","status":"Analyzed","description":"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).\n\nPatches: Fixed in webpack-dev-server@5.2.5.\n\nWorkarounds: 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_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L","score":4.3},"cwes":["CWE-346","CWE-441"],"references":["https://cna.openjsf.org/security-advisories.html","https://github.com/facebook/create-react-app/pull/7444","https://github.com/vuejs/vue-cli/commit/72ba7505aff2a8314e82aa5082379a77504a1fcb","https://github.com/webpack/webpack-dev-server/pull/4316","https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-mx8g-39q3-5c79"],"products":["webpack.js:webpack-dev-server"],"source":"nvd","synced_at":"2026-10-19T22:38:48.522727527+00:00"},"epss":{"cve":"CVE-2026-9595","score":0.00163,"percentile":0.05469,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-mx8g-39q3-5c79","url":"https://osv.dev/vulnerability/GHSA-mx8g-39q3-5c79","summary":"webpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies","modified":"2026-09-10T03:51:09.136558749Z","packages":[{"ecosystem":"npm","name":"webpack-dev-server","purl":"pkg:npm/webpack-dev-server","ranges":["<5.2.5"],"fixed":["5.2.5"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}