Vulnerability in webpack-dev-server (CVE-2026-6402)
Summary
Vulnerability in webpack-dev-server (CVE-2026-6402). Confidential information can be exposed externally. Mitigation: upgrade to 5.2.4 or later.
Original description
The description as published by the source.
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: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-6402 has been found in webpack-dev-server.
Confidential information can be exposed externally. CVSS score: 5.3/10.
What to do: upgrade webpack-dev-server to 5.2.4 or later.
If unsure, ask your IT team or search "webpack-dev-server CVE-2026-6402" on the vendor's site.
CVE-2026-6402 (webpack-dev-server) — CWE-749 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated
Patched: 5.2.4 — apply immediately
Workaround: Run the dev server with HTTPS enabled (--https or server.type: 'https' in config).
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-749) exists in webpack-dev-server.
Check the vendor advisory for the affected versions of webpack-dev-server.
Severity: Medium (CVSS 5.3/10). Confidential information can be exposed externally.
Update to 5.2.4.
Workaround: Run the dev server with HTTPS enabled (--https or server.type: 'https' in config).
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'webpack-dev-server' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'webpack-dev-server' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
webpack-dev-serverを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply temporary workaround mitigate
Run the dev server with HTTPS enabled (`--https` or `server.type: 'https'` in config).パッチが適用されるまでの応急処置として、Run the dev server with HTTPS enabled (
--httpsorserver.type: 'https'in config). を実施。回避策の副作用 (機能低下) を確認した上で。 -
3Apply patch patch
Upgrade webpack-dev-server to 5.2.4ステージング環境で 5.2.4 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
4Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory cna.openjsf.org
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- web github.com
- web github.com
- web github.com