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No exploitation reportedFix available

CVE-2026-9595

No exploitation reported by the sources we read.

  • Published2026-06-15
  • Fixed in5.2.5
  • WeaknessCWE-346 · CWE-441

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC
  1. 2026-06-1516:16CVE publishedNVD

Versions per branch

NVD · OSV
Webpack.js webpack-dev-server
BranchAffectedFixed in
5.2< 5.2.55.2.5

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA1 product

As openjs, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • webpack-dev-serverother versions: not affected
    Affected
    • < 5.2.5fixed in 5.2.5semver

    Not affected = 5.2.5

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-06-15

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • @rootio/webpack-dev-serverRoot:npmall versions · fixed in 4.10.0-root.io.2
  • @rootio/webpack-dev-serverRoot:npmall versions · fixed in 3.11.3-root.io.3
  • @rootio/webpack-dev-serverRoot:npmall versions · fixed in 3.11.3-root.io.4
  • @rootio/webpack-dev-serverRoot:npmall versions · fixed in 4.10.0-root.io.3
  • @rootio/webpack-dev-serverRoot:npmall versions · fixed in 5.0.4-root.io.1
  • @rootio/webpack-dev-serverRoot:npmall versions · fixed in 5.0.4-root.io.2
  • @rootio/webpack-dev-serverRoot:npmall versions · fixed in 5.2.2-root.io.2
  • @rootio/webpack-dev-serverRoot:npmall versions · fixed in 5.2.2-root.io.3

63 more package ranges on OSV.dev

Vendor advisories

  • CVE-2026-9595 Red Hat Product Security41 products fixed · 23 known affected

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

    workload-availability/node-healthcheck-must-gather-rhel9 as a component of Node HealthCheck Operator · workload-availability/node-healthcheck-operator-bundle as a component of Node HealthCheck Operator · workload-availability/node-healthcheck-rhel9-operator as a component of Node HealthCheck Operator · +20 more

  • RHSA-2026:66545 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: Red Hat AMQ Broker 7.13.6 release and security update

  • RHSA-2026:66488 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: Red Hat AMQ Broker 7.14.1 release and security update

  • RHSA-2026:57408 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: OpenShift Container Platform 4.19.44 bug fix and security update

  • RHSA-2026:59155 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: Red Hat Ansible Automation Platform 2.6 Container Release Update

  • RHSA-2026:59153 Red Hat Product Security2 products fixed

    Red Hat Security Advisory: Red Hat Ansible Automation Platform 2.7 Container Release Update

12 more advisories

Full record on NVD

Fix

  1. Update Webpack.js webpack-dev-server to 5.2.5
  2. Vendor fix Red Hat Product Security RHSA-2026:66545 · 1 productBefore applying the update, back up your existing installation, including all applications, configuration files, databases and database settings. The References section of this erratum contains a download link (you must log in to download the update).
  3. Vendor fix Red Hat Product Security RHSA-2026:57408 · 4 productsFor OpenShift Container Platform 4.19 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this asynchronous errata update: https://docs.redhat.com/en/documentation/openshift_container_platform/4.…
  4. Vendor fix Red Hat Product Security RHSA-2026:59155 · 4 productsBefore applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://docs.redhat.com/en/documentation/red_hat_ansible_automation_platform/2.6#Upgrade
  5. Vendor fix Red Hat Product Security RHSA-2026:59153 · 2 productsBefore applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://docs.redhat.com/en/documentation/red_hat_ansible_automation_platform/2.7#Upgrade
  6. Vendor fix Red Hat Product Security RHSA-2026:57590 · 2 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
  7. Vendor fix Red Hat Product Security RHSA-2026:56357 · 1 productFor more about Ansible plugins for Red Hat Developer Hub, see References links

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • CISA-ADPSSVC decisionnone2026-06-15
  • CNACVSS 3.15.3known since 2026-10-23
  • NVDCVSS 3.14.3read 2026-10-23
  • CNAweakness (CWE)CWE-346, CWE-441known since 2026-10-23
  • FIRST EPSSEPSS score0.2 %2026-11-08
  • OSVaffected packages—
  • GitHub AdvisoriesadvisoryMODERATE2026-06-17

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Published
2026-06-15
Last Modified
2026-06-17
NVD status
Analyzed
GitHub Advisory
GHSA-mx8g-39q3-5c79

Frequently asked questions

What is CVE-2026-9595?

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.

Is CVE-2026-9595 actively exploited?

Active exploitation of CVE-2026-9595 has not been confirmed. Its EPSS score was 0.2% on 2026-11-08, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-9595?

CVE-2026-9595 has a CVSS v3 base score of 4.3 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L.

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