VulnerabilityAnalyzed

CVE-2025-6543

Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability

KEVCRITICAL 9.2EPSS 10.1%

Does this matter?

Known to be exploited in the wild (CISA KEV, CISA remediation deadline 21 July 2025). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.

Description

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

CVSS 4.0: 9.2 CRITICALCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
EPSS: 10.09% probability · 95th percentile
CISA KEV: Listed 30 June 2025 · due 21 July 2025
Weakness: CWE-119
Affected: citrix/netscaler application delivery controller · citrix/netscaler gateway
Source: secure@citrix.com

CISA notes

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. https://support.citrix.com/support-home/kbsearch/article?articleNumber=CTX694788 ; https://www.netscaler.com/blog/news/netscaler-critical-security-updates-for-cve-2025-6543-and-cve-2025-5777/ ; https://nvd.nist.gov/vuln/detail/CVE-2025-6543

References

https://support.citrix.com/support-home/kbsearch/article?articleNumber=CTX694788Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-6543US Government Resource

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.