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Fencer Intel
medium 5.3

CVE-2026-6402 json

webpack-dev-server vulnerable to cross-origin source code exposure on non-HTTPS origins

published 6mo ago modified 8h ago also EUVD-2026-29404 , GHSA-79cf-xcqc-c78w

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 21%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm webpack-dev-server 5.2.4
  • webpack-dev-server webpack-dev-server 5.2.4
  • agama-web-ui openSUSE Tumbleweed 21+360.16caae772-44.1

opensuse advisories openSUSE-SU-2026:10979-1

Is CVE-2026-6402 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2026-6402 updated cvss 5.3

webpack-dev-server: webpack-dev-server: Information disclosure due to cross-origin source code exposure

  • Red Hat Cryostat 4 webpack-dev-server, cryostat-openshift-console-plugin-npm Red Hat Gatekeeper 3 gatekeeper/gatekeeper-rhel9 Red Hat Migration Toolkit for Containers rhmtc/openshift-migration-ui-rhel8 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 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
    +13 more products
    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 Red Hat AMQ Broker 7 webpack-dev-server Red Hat Ansible Automation Platform 2 automation-eda-controller, ansible-automation-platform-26/gateway-rhel9, ansible-automation-platform-24/lightspeed-rhel8, ansible-automation-platform-25/lightspeed-rhel8, ansible-automation-platform-26/lightspeed-rhel9 Red Hat build of Apache Camel - HawtIO 4 webpack-dev-server Red Hat build of Apache Camel for Spring Boot 4 webpack-dev-server Red Hat build of Apicurio Registry 2 webpack-dev-server Red Hat Build of Podman Desktop rh-podman-desktop.git Red Hat Data Grid 8 webpack-dev-server Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9 Red Hat Discovery 2 discovery/discovery-ui-rhel9 Red Hat Enterprise Linux 8 pcs, grafana, pcs-snmp, grafana-loki, grafana-mssql, grafana-mysql, +10 more Red Hat Enterprise Linux 9 pcs, grafana, pcs-snmp, grafana-selinux, js-d3-flame-graph
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux 10 pcs, grafana, js-d3-flame-graph
    affected: no fix available, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/disk-image-cuda-rhel9 Red Hat Fuse 7 webpack-dev-server Red Hat OpenShift AI (RHOAI) rhoai/odh-mlflow-rhel9 Red Hat OpenShift Container Platform 4 openshift4/ose-console-rhel9 Red Hat OpenShift Virtualization 4 container-native-virtualization/kubevirt-console-plugin, container-native-virtualization/kubevirt-console-plugin-rhel9 Red Hat Process Automation 7 webpack-dev-server
    +2 more products
    Red Hat Quay 3 quay/quay-rhel8 Red Hat Self-service automation portal 2 ansible-automation-platform/automation-portal
    affected: no fix available “Fix deferred”

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
no
Technical impact
partial
Assessed
5mo ago

Exploit prediction

0.29% chance of exploitation in the next 30 days, higher than 21% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

Affected packages

ecosystem package affected fixed in
npm webpack-dev-server
<5.2.4
5.2.4

Affected products

  • webpack-dev-server webpack-dev-server

Classification

Weakness
  • CWE-749 Exposed Dangerous Method or Function

References

Sources

Fencer Intel 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.

The maintainers of webpack/webpack-dev-server published their own advisory on GitHub. Reviewed sources take precedence over it.