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CVE-2025-6543

Critical CVSS 9.8 Known exploited

Published 2025-06-25 · last changed 2026-06-17 · added to CISA KEV 2025-06-30

This one is being exploited in the wild.

CISA added CVE-2025-6543 to the Known Exploited Vulnerabilities catalog on 2025-06-30. Federal agencies are required to remediate it on a deadline. If you have affected machines, this is the class of finding that moves ahead of the rest of the queue.

The fix

We hold no Microsoft remediation data for CVE-2025-6543, which normally means it is not a Windows CVE. For non-Microsoft software the fix is the vendor's own updated release, and the affected versions are listed below.

What it is

Memory overflow vulnerability leading to unintended control flow and Denial of Service in NetScaler ADC and NetScaler Gateway when configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server

Sources

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H