June 26, 2025 by Anil Shetty netscaler.com
Over the past two weeks, Cloud Software Group has released builds to address CVE-2025-6543 and CVE 2025-5777, which affect NetScaler ADC and NetScaler Gateway if they are configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR an Authentication Authorization and Auditing (“AAA”) virtual server. While both of the vulnerabilities involve the same modules, the exposures differ. CVE 2025-6543, if exploited, could lead to a memory overflow vulnerability, resulting in unintended control flow and Denial of Service. CVE 2025-5777 arises from insufficient input validation that leads to memory overread.

Some commentators have drawn comparisons between CVE 2025-5777 and CVE 2023-4966. While the vulnerabilities share some characteristics, Cloud Software Group has found no evidence to indicate that they are related.

The description of the vulnerability on the NIST website for CVE-2025-5777 initially erroneously identified NetScaler Management Interface as implicated in the vulnerability, but they subsequently updated the description to exclude it. The most accurate description of CVE 2025-5777 can be found in the Citrix security bulletin published on June 17, 2025.

Through our internal review process and by collaborating with customers, we identified the affected NetScaler ADC and NetScaler Gateway builds. CVE 2025-5777 only applies to customer-managed NetScaler ADC and NetScaler Gateway. Cloud Software Group upgrades Citrix-managed cloud services and Citrix-managed Adaptive Authentication with the necessary software updates. Please refer to the security bulletin for more details.

Citrix has signed CISA’s Secure by Design pledge, reinforcing our commitment to building security into every stage of the product lifecycle. As part of this pledge, we prioritize security by default, transparency, and accountability in how we manage vulnerabilities. Our Product Security Incident Response Team (PSIRT) follows industry standards to assess, address, and disclose vulnerabilities responsibly. We work closely with security researchers, government agencies and customers to ensure timely fixes and clear communication. Learn more about our responsible disclosure process at Citrix Vulnerability Response.

Additionally, there’s an issue related to authentication that you may observe after upgrading NetScaler to build 14.1 47.46 or 13.1 59.19. This can manifest as a “broken” login page, especially when using authentication methods like DUO configurations based on Radius authentication, SAML, or any Identity Provider (IDP) that relies on custom scripts. This behavior can be attributed to the Content Security Policy (CSP) header being enabled by default in this NetScaler build, especially when CSP was not enabled prior to the upgrade. For more information on this issue please refer to the KB article.