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Exploited vulnerability · CISA KEV

Is CVE-2025-6543 exploited? Yes: in CISA KEV since 30 Jun 2025

Gociux · Citrix NetScaler ADC and Gateway · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2025-6543, Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 30 Jun 2025, 5 days after it was published. It affects Citrix NetScaler ADC and Gateway, an internet-facing product of the kind attackers use for initial access. If you run it, CISA's required action is: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

exploitedYesCISA KEV · 30 Jun 2025
ransomwareNot knownno confirmed use
EPSStop 5%very likely to be exploited
severity9.2CVSS 4.0 · critical
US federal due21 Jul 2025BOD 22-01 deadline

What it is

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.

VendorCitrix (27 exploited CVEs in KEV)
ProductNetScaler ADC and Gateway
VulnerabilityCitrix NetScaler ADC and Gateway Buffer Overflow Vulnerability
WeaknessCWE-119
Published25 Jun 2025
Added to KEV30 Jun 2025
Reported by (CNA)Citrix

What to do

  1. Check whether you run it. Look for NetScaler ADC and Gateway in your asset inventory, including appliances and cloud images. Stack check lists every exploited Citrix CVE at once.
  2. Apply the fix. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
  3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 25 Jun 2025.
  4. Get told next time. Email alerts when CISA adds a CVE for Citrix.

Other exploited CVEs in NetScaler ADC and Gateway

References

Questions

Is CVE-2025-6543 being exploited?

Yes. CISA added CVE-2025-6543 to the Known Exploited Vulnerabilities catalog on 30 Jun 2025, which means there is reliable evidence of exploitation in the wild.

Is CVE-2025-6543 used in ransomware attacks?

CISA does not list known ransomware use for it. That can change, and exploitation alone is reason to fix it first.

How do I fix CVE-2025-6543?

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Check Citrix's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected NetScaler ADC and Gateway and watch it for signs of compromise.

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in June 2025 · Citrix scorecard · act-now radar.

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