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TI-2026-79248 Aliases CVE-2026-112085

Missing Origin checks on proxied WebSockets in webpack-dev-server

Priority LOW 35CWE-1385Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Security bypass
Confidentiality · integrity · availability
High · Low · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-346.

Summary

webpack-dev-server before 5.2.7 and from 6.0.0 before 6.1.0 are affected when a proxy entry forwards WebSockets. The server forwards non-HMR WebSocket upgrade requests to the proxy target without validating the Host or Origin headers (CWE-1385), so allowedHosts does not protect them. A malicious web page opened by a developer can open a cross-origin WebSocket through the dev server and read from and write to the proxied backend, even when the server is bound to loopback.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

webpack-dev-server is a development server that provides live reloading for webpack projects. In versions before 5.2.7 and in version 6.0.0, when a proxy entry is configured to forward WebSockets, the server forwards non-HMR WebSocket upgrade requests to the proxy target without validating the Host or Origin headers, so the allowedHosts protection does not apply to those proxied upgrades. A malicious web page visited by a developer can open a cross-origin WebSocket through the dev server and read from and write to the proxied backend, even when the server is bound to loopback. The issue is fixed in webpack-dev-server 5.2.7 and 6.1.0, where proxied WebSocket upgrades pass the same Host and Origin validation as the HMR WebSocket, and users should upgrade to one of those versions or later. As a workaround, omit WebSocket forwarding from proxy entries that do not need it and scope the proxy to specific paths.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00147 3rd percentileScored 2026-11-07
Fix Fixed webpack-dev-server (webpack-dev-server): 5.2.7, 6.1.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
webpackwebpack-dev-serverbefore 5.2.7; 6.0.0 to before 6.1.05.2.7, 6.1.0Patch availableCNA
  • webpack-dev-server Vendorwebpack Affected before 5.2.7; 6.0.0 to before 6.1.0 Fixed in 5.2.7, 6.1.0 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:webpack.js:webpack-dev-server:*:*:*:*:*:*:*:*before 5.2.7; 6.0.0 to before 6.1.0Vulnerablewebpack
  • cpe:2.3:a:webpack.js:webpack-dev-server:*:*:*:*:*:*:*:* Versions before 5.2.7; 6.0.0 to before 6.1.0 Vulnerable ·webpack

Remediation

Upgrade to webpack-dev-server 5.2.7 or 6.1.0 or later, where proxied WebSocket upgrades get the same Host and Origin validation as the HMR WebSocket. As a workaround, omit WebSocket forwarding from proxy entries that do not need it and scope each proxy to specific paths.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

  • Fix · CNA webpack-dev-server (webpack-dev-server) Fixed in 5.2.7, 6.1.0

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    webpack-dev-server 5.2.7, 6.1.0

    2 records Highest priority Priority LOW 2 LOW

    Other records, highest priority first

    • TI-2026-79254 Host validation bypass in webpack-dev-server leaks stack tracesPriority LOW 30
    Show all 2 records →

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat Hardened Images

Timeline

  1. 2026-10-22 Threatist record created from CVE-2026-112085
  2. 2026-10-22 CISA SSVC decision points changed
  3. 2026-10-22 Priority changed: MEDIUM → LOW
  4. 2026-10-23 Affected versions changed · Red Hat
  5. 2026-10-23 CVSS score added · Red Hat

References

Advisory 2

  • TI-2025-21666 Origin validation error in webpack-dev-server CVSS 3.1MEDIUM 6.5
  • TI-2025-21665 webpack-dev-server users' source code may be stolen when they access a malicious web site CVSS 3.1MEDIUM 5.9
  • TI-2018-10580 An issue was discovered in lib/Server.js in webpack-dev-server before 3.1.6. CVSS 3.0HIGH 7.5
  • TI-2026-12328 webpack-dev-server vulnerable to denial of service via a malformed Host or Origin header CVSS 3.1MEDIUM 5.3
  • TI-2026-79254 Host validation bypass in webpack-dev-server leaks stack traces CVSS 3.1MEDIUM 5.3
  • TI-2026-08430 webpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies CVSS 3.1MEDIUM 5.3
See all 8 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences