Medium [CVE-2026-14631] Denial of Service via malformed headers
This medium-severity Red Hat Linux advisory covers CVE-2026-14631.
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Summary
webpack-dev-server versions 5.2.5 and earlier terminate the whole Node.js process when an unauthenticated peer sends either a normal HTTP request with a malformed Host header or a WebSocket upgrade to the default /ws endpoint with a malformed Origin header.
The malformed value causes an uncaught exception in the host-validation path and crashes the dev server. Impact is limited to availability of the development server, no data disclosure, no code execution.
Workarounds: keep the dev server bound to localhost (the default) and do not expose it to untrusted networks. This malformed input causes an uncaught exception, leading to the termination of the Node.js process and crashing the development server.
This vulnerability results in a Denial of Service (DoS), impacting the availability of the development server. webpack-dev-server is a development-time tool used to serve files during local frontend development and is not started or executed in production deployments.
While the package may appear in SBOM manifests due to its presence in build-stage node_modules, the webpack-dev-server process is not running in shipped container images or installed RPM packages, so the vulnerable code path (host/origin header validation) cannot be reached by an attacker in a production environment.
Red Hat severity: Moderate — CVSS 4.3 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 12 days ago·verify at source
- 5.2.5
- 5.2.6
Official advisory · high-confidence parse· fetched 12 days ago·verify at source
Mitigation checklist
- webpack-dev-server should never be exposed to untrusted networks. By default, it binds to localhost only. Users who run webpack-dev-server during development should ensure it remains bound to localhost and upgrade to version 5.2.6 or later, which fixes the malformed header handling.
Official advisory · high-confidence parse· fetched 12 days ago·verify at source
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