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
4.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 4.3Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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
4.3(medium)
EPSS
5.8%
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(1)

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

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
webpack-dev-server—5.2.5—

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 13× in last 7d / 45× 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.

  1. 2026-07-07 00:24 UTCEG score recompute
  2. 2026-07-06 16:27 UTCEPSS rescore
  3. 2026-07-06 02:23 UTCEPSS rescore
  4. 2026-07-05 09:26 UTCEG score recompute
  5. 2026-07-05 02:31 UTCEPSS rescore
  6. 2026-07-04 10:05 UTCEG score recompute
  7. 2026-07-04 06:31 UTCEPSS rescore
  8. 2026-07-03 07:42 UTCEG score recompute
  9. 2026-07-02 09:29 UTCEG score recompute
  10. 2026-07-01 15:07 UTCEPSS rescore
  11. 2026-07-01 11:15 UTCEG score recompute
  12. 2026-06-30 23:22 UTCEPSS rescore
  13. 2026-06-30 13:02 UTCEG score recompute
  14. 2026-06-29 14:06 UTCEPSS rescore
  15. 2026-06-29 13:41 UTCEG score recompute
  16. 2026-06-28 15:28 UTCEG score recompute
  17. 2026-06-28 14:07 UTCEPSS rescore
  18. 2026-06-28 04:56 UTCEPSS rescore
  19. 2026-06-27 17:15 UTCEG score recompute
  20. 2026-06-27 03:08 UTCEPSS rescore
  21. 2026-06-26 19:02 UTCEG score recompute
  22. 2026-06-25 20:49 UTCEG score recompute
  23. 2026-06-25 13:50 UTCEPSS rescore
  24. 2026-06-24 22:35 UTCEG score recompute
  25. 2026-06-24 14:05 UTCEPSS rescore
Show 20 more
  1. 2026-06-24 00:22 UTCEG score recompute
  2. 2026-06-23 21:33 UTCEPSS rescore
  3. 2026-06-23 02:02 UTCEG score recompute
  4. 2026-06-22 14:25 UTCEPSS rescore
  5. 2026-06-22 03:47 UTCEG score recompute
  6. 2026-06-21 14:56 UTCEPSS rescore
  7. 2026-06-21 05:31 UTCEG score recompute
  8. 2026-06-21 01:59 UTCEPSS rescore
  9. 2026-06-20 07:14 UTCEG score recompute
  10. 2026-06-19 19:26 UTCEPSS rescore
  11. 2026-06-19 09:00 UTCEG score recompute
  12. 2026-06-18 17:52 UTCEPSS rescore
  13. 2026-06-18 10:46 UTCEG score recompute
  14. 2026-06-17 17:53 UTCEPSS rescore
  15. 2026-06-17 12:29 UTCEG score recompute▼ 1.00
  16. 2026-06-16 17:53 UTCEPSS rescore
  17. 2026-06-16 17:47 UTCNVD updateCVSS v3 → 4.3
  18. 2026-06-16 14:16 UTCEG score recompute
  19. 2026-06-15 16:04 UTCEG score recompute
  20. 2026-06-15 16:03 UTCMITRE cvelistV5first tracked

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 in the National Vulnerability Database 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 5.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
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?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-9595, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-9595

Explore →

Is Your Infrastructure Affected by CVE-2026-9595?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs