What is CVE-2025-6543?

CVE-2025-6543 is a critical-severity vulnerability in Citrix Netscaler Application Delivery Controller, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.8/10. Published 2025-06-25.

How severe is CVE-2025-6543?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2025-6543 known to be exploited?

Yes. CVE-2025-6543 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2025-06-30), indicating it is being actively exploited. 20 public proof-of-concept repositories are indexed.

Buffer overflow in Citrix Netscaler Application Delivery Controller

CVE-2025-6543

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

Vulnerability class: Buffer Overflow

Published 2025-06-25 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.106 (95.7th percentile), scored 2026-10-18.

Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 96th percentile — 95.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.101 · newest: 0.106 · change: +0.004

Affected products

Citrix Netscaler Application Delivery Controller
Citrix Netscaler Gateway
Netscaler Adc — versions 14.1, 13.1, 13.1 FIPS and NDcPP
Netscaler Gateway — versions 14.1, 13.1, 13.1 FIPS and NDcPP

Weakness classification (CWE)

CWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2025-06-30. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2025-07-21.

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.

Public proof-of-concept exploits

References

support.citrix.com/support-home/kbsearch/article (Vendor Advisory)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)

Frequently asked questions

What is CVE-2025-6543?: CVE-2025-6543 is a critical-severity vulnerability in Citrix Netscaler Application Delivery Controller, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.8/10. Published 2025-06-25.
How severe is CVE-2025-6543?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2025-6543 known to be exploited?: Yes. CVE-2025-6543 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2025-06-30), indicating it is being actively exploited. 20 public proof-of-concept repositories are indexed.