CVE-2026-95955.3MediumCWE-346

CVE-2026-9595: webpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies

webpack-dev-server

Vendor fix available · Affected: webpack-dev-server · Exploitation: unlikely (under 1%)

Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.

0.2%probability of exploitation in the next 30 days

5th percentile

050100

Higher than 5% of scored CVEs

5.3MediumCVSS 3.1

LowMediumHighCrit.

DescriptionCVE.org

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.

Affected products1

From the CVE record. A product or version that is not listed is unknown, not unaffected.

webpack-dev-server · webpack-dev-serverbefore 5.2.5

On the Atlas

Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.

Open the Atlas

Exploitation: Unlikely (under 1%). EPSS under 1%, or no score yet.
CISA KEV: Not listed
Public check: No public nuclei template
Weakness: Origin Validation Error · Access Control
Vendor: webpack-dev-server
Published: June 2026
Band: Unlikely (under 1%), June 2026

CoverageNo articles yet

No CyberSIXT article names CVE-2026-9595 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.