CVE-2025-6543: in the CISA KEV catalogue

Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability. CISA added CVE-2025-6543 to the Known Exploited Vulnerabilities catalogue on 2025-06-30 with a default due date of 2025-07-21. Known ransomware campaign use: Unknown. Forensic triage flag: No.

Citrix NetScaler ADC and Gateway contain a buffer overflow vulnerability leading to unintended control flow and Denial of Service. NetScaler must be configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server. (CISA description)

Vendor / product: Citrix NetScaler ADC and Gateway
CWE: CWE-119
CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
EPSS: 10%, percentile 95 (scored 2026-11-03)

EPSS puts about 10 in 100 odds (10%) on exploitation activity being observed in the next 30 days. Its score is higher than or equal to that of 95% of scored CVEs. This is a model estimate about exploitation anywhere, not about your environment.

Vendor and reference links (from CISA)

Your own deadline under CISA BOD 26-04 depends on exposure, automatability and technical impact: work it out with the BOD 26-04 calculator.

Data dates. CISA KEV catalogue version 2026.11.03, released 2026-11-03, 1,767 entries (checked 2026-11-03). EPSS model v2026.06.15, scored 2026-11-03, 399,388 CVEs. Sources: CISA and FIRST (EPSS by FIRST; scores generated by Empirical Security). Copied to our own database and refreshed automatically; if a refresh fails, the previous copy keeps serving with its own date.

Frequently asked questions

Is CVE-2025-6543 in the CISA KEV catalogue?

Yes. CISA added CVE-2025-6543 (Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability) to the Known Exploited Vulnerabilities catalogue on 2025-06-30. CISA's default due date for it is 2025-07-21.

Is CVE-2025-6543 used in ransomware attacks?

CISA marks known ransomware campaign use as Unknown for CVE-2025-6543. That means CISA lacks confirmation, not that ransomware groups do not use it.

What should I do about CVE-2025-6543?

CISA's required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Sources

CISA, Known Exploited Vulnerabilities Catalog (accessed 2026-11-03)
FIRST, Exploit Prediction Scoring System (EPSS) (EPSS by FIRST; scores generated by Empirical Security)
NVD record for CVE-2025-6543