CVE-2026-9595

MEDIUMNVD 4.34.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 4.3 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 94% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
4.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 4.3Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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 [email protected].

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.

CVSS v3
4.3
EG Score
4.3MEDIUMmedium confidence
EG Risk
24
EG Risk 24/100

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity43% × 45%
Exploitation0% × 40%
Automatability30% × 15%
EPSS PROB
0.2%
EPSS %ILE
12th
KEV
Not listed

Published

June 15, 2026

Last Modified

June 16, 2026

Advisory Details (5)

Auto-updated Jun 15, 2026
Patch available. Sources: github_pr, github_commit, github.
github Patch Available

webpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies · Advisory · webpack/webpack-dev-server · GitHub

https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-mx8g-39q3-5c79
github_pr Patch Available

fix: skip HMR websocket path when forwarding upgrades to user-defined proxies

Patch available: webpack/webpack-dev-server v5.2.5 (PR #4316 merged 2026-05-25)

https://github.com/webpack/webpack-dev-server/pull/4316
github_commit Patch Available

commit 72ba7505aff2 (vuejs/vue-cli)

Patch available: vuejs/vue-cli v4.5.12 (contains commit 72ba7505aff2)

https://github.com/vuejs/vue-cli/commit/72ba7505aff2a8314e82aa5082379a77504a1fcb
github_pr Patch Available

Fix for #6720: HMR not working in Firefox if proxy option present

Patch available: facebook/create-react-app v3.1.0 (PR #7444 merged 2019-08-07)

https://github.com/facebook/create-react-app/pull/7444
generic

Security Advisories | OpenJS Foundation CVE Numbering Authority

https://cna.openjsf.org/security-advisories.html

Vendor Advisories for CVE-2026-9595(18)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(15)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatwebpack-dev-server2026-09-10redhat
redhatopenshift4/ose-console-rhel9:17870895232026-08-26redhat
redhatansible-automation-platform-26/gateway-rhel9:17872197512026-08-24redhat
redhatansible-automation-platform-27/gateway-rhel9:17872184092026-08-24redhat
redhatrh-podman-desktop-0:1.1.2-1.el10_22026-08-20redhat
redhatansible-automation-platform/automation-portal:17870471882026-08-18redhat
redhatansible-automation-platform/automation-portal:17870471142026-08-18redhat
redhatdiscovery/discovery-ui-rhel9:17866348252026-08-13redhat
redhatopenshift4/ose-agent-installer-ui-rhel9:17859108962026-08-11redhat
redhatansible-automation-platform-26/lightspeed-rhel9:17857753602026-08-04redhat
redhatansible-automation-platform-25/lightspeed-rhel8:17854301742026-08-04redhat
redhatrhmtc/openshift-migration-ui-rhel8:17836905322026-07-20redhat
redhatopenshift4/ose-console-rhel9:17835023382026-07-14redhat
redhatopenshift4/ose-console-rhel9:17836023262026-07-14redhat
redhatopenshift4/ose-console-rhel9:17829136212026-07-07redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFix by version rangeDependents
webpack-dev-server—
  • every version up to 5.2.5: fixed in 5.2.5
—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 30× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 175 total refreshes for this CVE.

  1. 2026-10-04 23:23 UTCEPSS rescore
  2. 2026-10-03 14:26 UTCEPSS rescore
  3. 2026-10-03 07:39 UTCOSV refresh
  4. 2026-10-02 17:57 UTCEPSS rescore
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  11. 2026-09-26 15:59 UTCEPSS rescore
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  21. 2026-09-15 03:12 UTCEPSS rescore
  22. 2026-09-14 03:47 UTCEG score recompute
  23. 2026-09-14 03:47 UTCVendor advisory
  24. 2026-09-13 16:48 UTCEPSS rescore
  25. 2026-09-12 15:02 UTCEPSS rescore
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  1. 2026-09-11 09:38 UTCEPSS rescore
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  5. 2026-09-05 15:31 UTCEPSS rescore
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  7. 2026-09-02 14:12 UTCEPSS rescore
  8. 2026-09-01 13:54 UTCEPSS rescore
  9. 2026-09-01 04:40 UTCEPSS rescore
  10. 2026-08-30 22:59 UTCEG score recompute
  11. 2026-08-30 22:59 UTCVendor advisory
  12. 2026-08-30 19:18 UTCEPSS rescore
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  18. 2026-08-24 23:38 UTCEG score recompute
  19. 2026-08-24 23:38 UTCVendor advisory
  20. 2026-08-24 14:18 UTCEPSS rescore
  21. 2026-08-23 09:49 UTCEG score recompute
  22. 2026-08-23 09:49 UTCVendor advisory
  23. 2026-08-23 00:19 UTCEPSS rescore
  24. 2026-08-21 23:49 UTCEPSS rescore
  25. 2026-08-21 09:54 UTCEG score recompute
  26. 2026-08-21 09:54 UTCVendor advisory
  27. 2026-08-20 22:56 UTCEPSS rescore
  28. 2026-08-20 11:29 UTCEG score recompute
  29. 2026-08-20 11:29 UTCVendor advisory
  30. 2026-08-19 17:04 UTCEPSS rescore
  31. 2026-08-19 13:15 UTCEG score recompute
  32. 2026-08-19 13:15 UTCVendor advisory
  33. 2026-08-18 13:49 UTCEPSS rescore
  34. 2026-08-17 13:47 UTCEPSS rescore
  35. 2026-08-16 22:35 UTCEG score recompute
  36. 2026-08-16 22:35 UTCVendor advisory
  37. 2026-08-16 14:56 UTCEPSS rescore
  38. 2026-08-16 02:15 UTCEPSS rescore
  39. 2026-08-16 00:22 UTCVendor advisory
  40. 2026-08-15 02:08 UTCEG score recompute
  41. 2026-08-15 02:08 UTCVendor advisory
  42. 2026-08-15 01:31 UTCEPSS rescore
  43. 2026-08-14 03:55 UTCEG score recompute
  44. 2026-08-14 03:55 UTCVendor advisory
  45. 2026-08-13 22:00 UTCEPSS rescore
  46. 2026-08-13 05:42 UTCEG score recompute
  47. 2026-08-13 05:42 UTCVendor advisory
  48. 2026-08-12 13:51 UTCEPSS rescore
  49. 2026-08-12 07:29 UTCEG score recompute
  50. 2026-08-12 07:29 UTCVendor advisory
  51. 2026-08-11 13:43 UTCEPSS rescore
  52. 2026-08-11 09:03 UTCEG score recompute
  53. 2026-08-11 09:03 UTCVendor advisory
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  56. 2026-08-10 10:50 UTCVendor advisory
  57. 2026-08-09 13:47 UTCEPSS rescore
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  59. 2026-08-09 12:37 UTCVendor advisory
  60. 2026-08-08 16:37 UTCEPSS rescore
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  62. 2026-08-08 14:24 UTCVendor advisory
  63. 2026-08-07 16:30 UTCEPSS rescore
  64. 2026-08-07 16:11 UTCVendor advisory
  65. 2026-08-06 17:58 UTCEG score recompute
  66. 2026-08-06 17:58 UTCVendor advisory
  67. 2026-08-06 13:47 UTCEPSS rescore
  68. 2026-08-05 19:45 UTCEG score recompute
  69. 2026-08-05 19:45 UTCVendor advisory
  70. 2026-08-05 19:17 UTCEPSS rescore
  71. 2026-08-04 15:42 UTCEG score recompute
  72. 2026-08-04 15:42 UTCVendor advisory
  73. 2026-08-04 15:10 UTCEPSS rescore
  74. 2026-08-04 10:39 UTCEPSS rescore
  75. 2026-08-03 10:36 UTCEPSS rescore

Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-9595?
CVE-2026-9595 is a medium vulnerability published on June 15, 2026. 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…
When was CVE-2026-9595 disclosed?
CVE-2026-9595 was first published on June 15, 2026, with the most recent update on June 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-9595 actively exploited?
CVE-2026-9595 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (12th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-9595?
CVE-2026-9595 has a CVSS v3 base score of 4.3 (NVD).
How do I remediate CVE-2026-9595?
A fix for CVE-2026-9595 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-9595 are linked in the Vendor Advisories panel on this page.

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