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Fencer Vulns
medium 5.3

CVE-2026-9595 json

webpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies

published 2026-06-15 4 mo ago modified 2026-09-10 1 mo ago also GHSA-mx8g-39q3-5c79 , EUVD-2026-36729

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 5%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm webpack-dev-server 5.2.5
  • webpack-dev-server webpack-dev-server 5.2.5
  • rh-podman-desktop RHEL 10.2 1.1.2-1.el10_2

red hat advisories RHSA-2026:57590

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-9595 updated cvss 7.1

webpack-dev-server: webpack-dev-server: Information disclosure and denial of service via improper proxy configuration

  • Red Hat Node HealthCheck Operator workload-availability/node-healthcheck-rhel9-operator, workload-availability/node-healthcheck-operator-bundle, workload-availability/node-healthcheck-must-gather-rhel9 Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-console-plugin-rhel9, openshift-lightspeed/lightspeed-console-plugin-419-rhel9, openshift-lightspeed/lightspeed-console-plugin-pf5-rhel9
    affected: workaround, no fix available
  • Red Hat OpenShift Pipelines openshift-pipelines/pipelines-hub-ui-rhel8, openshift-pipelines/pipelines-hub-ui-rhel9, openshift-pipelines/pipelines-console-plugin-rhel8, openshift-pipelines/pipelines-console-plugin-rhel9, openshift-pipelines/pipelines-console-plugin-pf5-rhel9
    affected: workaround, no fix available, no fix planned “Will not fix”
  • Red Hat Ansible Automation Platform 2 automation-eda-controller, ansible-automation-platform-24/lightspeed-rhel8
    affected: workaround, no fix planned “Will not fix”
  • Red Hat build of Apache Camel - HawtIO 4 webpack-dev-server
    affected: workaround, no fix available
  • Red Hat Build of Podman Desktop rh-podman-desktop.git
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Connectivity Link 1 rhcl-1/rhcl-console-plugin-rhel9
    affected: workaround, no fix available
  • Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/bootc-gaudi-rhel9, rhelai3/disk-image-cuda-rhel9
    affected: workaround, no fix planned “Will not fix”
  • Red Hat OpenShift Container Platform 5 openshift5/ose-console-rhel9, openshift5/ose-agent-installer-ui-rhel9
    affected: workaround, no fix available
show 25 more
  • Red Hat Quay 3 quay/quay-rhel8
    affected: workaround, no fix planned “Will not fix”
  • Red Hat AMQ Broker 7.13.6
    fixed: vendor fix RHSA-2026:66545
  • Red Hat AMQ Broker 7.14.1
    fixed: vendor fix RHSA-2026:66488
  • Red Hat Ansible Automation Platform 2.1 ansible-automation-platform/automation-portal 1787047114
    fixed: vendor fix RHSA-2026:56338
  • Red Hat Ansible Automation Platform 2.2 ansible-automation-platform/automation-portal 1787047188
    fixed: vendor fix RHSA-2026:56357
  • Red Hat Ansible Automation Platform 2.5 ansible-automation-platform-25/lightspeed-rhel8 1785430174
    fixed: vendor fix RHSA-2026:50357
  • Red Hat Ansible Automation Platform 2.6 ansible-automation-platform-26/gateway-rhel9 1787219751, ansible-automation-platform-26/lightspeed-rhel9 1785775360
    fixed: vendor fix RHSA-2026:59155
  • Red Hat Ansible Automation Platform 2.7 ansible-automation-platform-27/gateway-rhel9 1787218409
    fixed: vendor fix RHSA-2026:59153
  • Red Hat Data Grid 8.6.2
    fixed: vendor fix RHSA-2026:41951
  • Red Hat Discovery 2 discovery/discovery-ui-rhel9 1786634825
    fixed: vendor fix RHSA-2026:54760
  • Red Hat Enterprise Linux Extensions Channel (v. 10) rh-podman-desktop 1.1.2-1.el10_2
    fixed: vendor fix RHSA-2026:57590
  • Red Hat Migration Toolkit 1.8 rhmtc/openshift-migration-ui-rhel8 1783690532
    fixed: vendor fix RHSA-2026:41928
  • Red Hat OpenShift Container Platform 4.19 openshift4/ose-console-rhel9 1787089523
    fixed: vendor fix RHSA-2026:57408
  • Red Hat OpenShift Container Platform 4.20 openshift4/ose-console-rhel9 1783602326
    fixed: vendor fix RHSA-2026:37628
  • Red Hat OpenShift Container Platform 4.21 openshift4/ose-console-rhel9 1783502338
    fixed: vendor fix RHSA-2026:37186
  • Red Hat OpenShift Container Platform 4.22 openshift4/ose-console-rhel9 1782913621, openshift4/ose-agent-installer-ui-rhel9 1785910896
    fixed: vendor fix RHSA-2026:51038
  • Red Hat Cryostat 4 webpack-dev-server, cryostat-openshift-console-plugin-npm
    not affected: component not present
  • Red Hat Gatekeeper 3 gatekeeper/gatekeeper-rhel9
    not affected: vulnerable code not present
  • Red Hat OpenShift Service Mesh 2 openshift-service-mesh/kiali-rhel8, openshift-service-mesh/kiali-ossmc-rhel8 Red Hat OpenShift Service Mesh 3 openshift-service-mesh/kiali-rhel9, openshift-service-mesh/kiali-ossmc-rhel9, openshift-service-mesh/kiali-rhel9-operator, openshift-service-mesh/kiali-operator-bundle
    not affected: component not present
  • Red Hat Ansible Automation Platform 2 ansible-automation-platform-27/lightspeed-rhel9 Red Hat Ansible Automation Platform 2.5 ansible-automation-platform-25/hub-rhel8 1785376274, ansible-automation-platform-25/gateway-rhel8 1785374193, ansible-automation-platform-25/hub-web-rhel8 1785456973, ansible-automation-platform-25/receptor-rhel8 1785373835, ansible-automation-platform-25/controller-rhel8 1785376834, ansible-automation-platform-25/de-minimal-rhel8 1785383359, +20 more Red Hat Ansible Automation Platform 2.6 ansible-automation-platform-26/hub-rhel9 1785753568, ansible-automation-platform-26/hub-rhel9 1787220598, ansible-automation-platform-26/gateway-rhel9 1785780020, ansible-automation-platform-26/hub-web-rhel9 1785756951, ansible-automation-platform-26/hub-web-rhel9 1787224278, ansible-automation-platform-26/receptor-rhel9 1785632117, +54 more Red Hat Ansible Automation Platform 2.7 ansible-automation-platform-27/hub-rhel9 1787223293, ansible-automation-platform-27/hub-web-rhel9 1787225966, ansible-automation-platform-27/receptor-rhel9 1787216969, ansible-automation-platform-27/mcp-tools-rhel9 1787218205, ansible-automation-platform-27/controller-rhel9 1787220257, ansible-automation-platform-27/de-minimal-rhel9 1787224014, +25 more
    not affected: vulnerable code not present
  • Red Hat build of Apache Camel for Spring Boot 4 webpack-dev-server
    not affected: component not present
  • Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9
    not affected: vulnerable code not in execute path
  • Red Hat Discovery 2 discovery/discovery-server-rhel9 1786638573 Red Hat Enterprise Linux 8 pcs, grafana, pcs-snmp, grafana-loki, grafana-mssql, grafana-mysql, +12 more
    not affected: vulnerable code not present
  • Red Hat Enterprise Linux 9 pcs, grafana, pcs-snmp, grafana-selinux, js-d3-flame-graph Red Hat Enterprise Linux 10 pcs, grafana, js-d3-flame-graph
    not affected: component not present
  • Red Hat Fuse 7 webpack-dev-server
    not affected: vulnerable code not present

8 more not affected in the full advisory

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.16% chance of exploitation in the next 30 days, higher than 5% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
NVD 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected packages

ecosystem package affected fixed in
npm webpack-dev-server
<5.2.5
5.2.5

Affected products

  • webpack-dev-server webpack-dev-server

Classification

Weakness
  • CWE-346 Origin Validation Error
  • CWE-441 Unintended Proxy or Intermediary

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.