CISA has issued an pressing warning concerning a essential buffer overflow vulnerability in Citrix NetScaler ADC and Gateway merchandise, designated as CVE-2025-6543.
Added to CISA’s Identified Exploited Vulnerabilities (KEV) catalog on June 30, 2025, menace actors are actively exploiting this high-severity flaw and pose important dangers to organizations using these community infrastructure parts.
The vulnerability permits attackers to attain unintended management stream manipulation and execute Denial-of-Service (DoS) assaults towards affected programs, prompting speedy motion from federal businesses and personal sector organizations.
Citrix NetScaler Buffer Overflow Vulnerability
CVE-2025-6543 represents a buffer overflow vulnerability categorised beneath the Widespread Weak spot Enumeration (CWE) 119, which encompasses the improper restriction of operations inside reminiscence buffer boundaries.
This technical classification signifies that the vulnerability stems from inadequate enter validation mechanisms throughout the NetScaler codebase, permitting attackers to jot down knowledge past allotted reminiscence boundaries.
The exploitation of this flaw can lead to arbitrary code execution and system compromise, making it significantly harmful for internet-facing community home equipment.
The vulnerability particularly impacts Citrix NetScaler ADC (Utility Supply Controller) and Gateway merchandise when configured in particular operational modes.
These enterprise-grade community units function essential infrastructure parts, dealing with load balancing, SSL offloading, and safe distant entry functionalities for organizations worldwide.
The buffer overflow situation happens throughout packet processing routines, the place malformed community site visitors can set off reminiscence corruption, resulting in system instability or full compromise.
The vulnerability’s exploitation requires particular NetScaler configurations to be current, limiting its assault floor however nonetheless affecting a considerable variety of deployments.
Affected programs have to be configured as Gateway companies, together with VPN digital servers, ICA Proxy implementations, CVPN (Cloud VPN) companies, or RDP Proxy configurations.
Moreover, programs configured with AAA (Authentication, Authorization, and Accounting) digital servers are prone to this vulnerability.
Organizations using NetScaler units in these configurations face speedy dangers of service disruption, unauthorized entry, and potential lateral motion inside their community infrastructure.
Whereas CISA’s present evaluation signifies the vulnerability’s use in ransomware campaigns stays unknown, the energetic exploitation standing suggests subtle menace actors are leveraging this flaw for malicious functions.
Threat FactorsDetailsAffected ProductsCitrix NetScaler ADC and GatewayImpactDenial of Service (DoS)Exploit PrerequisitesNetScaler have to be configured as:- Gateway (VPN digital server, ICA Proxy, CVPN, RDP Proxy)- OR AAA digital serverCVSS Score9.2 (Important)
Mitigation
CISA has established a compulsory compliance deadline of July 21, 2025, requiring federal businesses to implement vendor-provided mitigations or discontinue use of weak merchandise.
This directive follows Binding Operational Directive (BOD) 22-01 tips, which mandate federal businesses to deal with identified exploited vulnerabilities inside specified timeframes.
Organizations should instantly apply safety updates launched by Citrix and observe steerage to guard towards ongoing threats.
For cloud service implementations, further BOD 22-01 cloud service steerage applies, requiring enhanced monitoring and incident response capabilities.
The pressing nature of this vulnerability underscores the essential significance of sustaining present patch ranges for community infrastructure parts and implementing sturdy vulnerability administration applications throughout enterprise environments.
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