How severe is CVE-2026-9595?

CVE-2026-9595 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2026-9595 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (6th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-9595?

CVE-2026-9595 affects Webpack.js Webpack-dev-server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-9595?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-9595 have an EU (EUVD) identifier?

Yes. CVE-2026-9595 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-36729.

When was CVE-2026-9595 published?

CVE-2026-9595 was published on 2026-06-15 and last updated on 2026-06-17.

CVE-2026-9595

CVE-2026-9595 is a medium-severity vulnerability in Webpack.js Webpack-dev-server with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-346.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
EPSS exploit prediction: 0% (6th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-36729
Weakness: CWE-346
Affected product: Webpack.js Webpack-dev-server
Published: 2026-06-15
Last modified: 2026-06-17

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 [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.

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 [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.
How severe is CVE-2026-9595?: CVE-2026-9595 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2026-9595 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (6th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-9595?: CVE-2026-9595 affects Webpack.js Webpack-dev-server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-9595?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-9595 have an EU (EUVD) identifier?: Yes. CVE-2026-9595 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-36729.
When was CVE-2026-9595 published?: CVE-2026-9595 was published on 2026-06-15 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:webpack.js:webpack-dev-server:*:*:*:*:*:*:*:*

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