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Citrix has issued security updates for a critical vulnerability in NetScaler ADC that has been actively exploited. The vulnerability CVE-2025-6543 has a CVSS score of 9.2, indicating high severity.
It’s a memory overflow issue that may cause control flow errors and denial-of-service. To exploit it, the appliance must be set up as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server.
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The shortcoming impacts the below versions –
NetScaler ADC and NetScaler Gateway 14.1 prior to 14.1-47.46
NetScaler ADC and NetScaler Gateway 13.1 prior to 13.1-59.19
NetScaler ADC and NetScaler Gateway 12.1 and 13.0 (vulnerable and end-of-life)
NetScaler ADC 13.1-FIPS and NDcPP prior to 13.1-37.236-FIPS and NDcPP
“Secure Private Access on-prem or Secure Private Access Hybrid deployments using NetScaler instances are also affected by the vulnerabilities,” Citrix said.
“Customers need to upgrade these NetScaler instances to the recommended NetScaler builds to address the vulnerabilities.”
The company did not reveal how the flaw is being exploited in real-world attacks, but said “exploits of CVE-2025-6543 on unmitigated appliances have been observed.”
The disclosure comes shortly after Citrix patched another critical-rated security flaw in NetScaler ADC (CVE-2025-5777, CVSS score: 9.3) that could be exploited by threat actors to gain access to susceptible appliances.
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