NetScaler

Security Advisory

Multiple Critical Vulnerabilities in Citrix NetScaler ADC/Gateway 

Security Advisory: Multiple vulnerabilities have been discovered in NetScaler ADC (formerly Citrix ADC) and NetScaler Gateway One Actively Exploited in Wild .

Citrix credited Jimi Sebree of Horizon3.ai, Jonathan Hetzer of Schramm & Partnerfor and Francois Hammerli for discovering and reporting the vulnerabilities.

Severity Critical 
CVSS Score 9.2 
CVEs CVE-2025-7775, CVE-2025-7776, CVE-2025-8424 
POC Available No 
Actively Exploited Yes 
Exploited in Wild Yes 
Advisory Version 1.0 

Overview 
A critical zero-day vulnerability, tracked as CVE-2025-7775, puts over 28,200 Citrix instances at risk worldwide.

This flaw allows attackers to run malicious code on affected systems without authentication. The issue is actively being exploited in the wild and immediate action is needed to secure systems.  Another two flaws were fixed in the latest updates.  

Vulnerability Name CVE ID Product Affected Severity 
Memory overflow vulnerability leading to RCE CVE-2025-7775 NetScaler ADC & Gateway 9.2 
Memory overflow vulnerability leading to unpredictable behavior CVE-2025-7776 NetScaler ADC & Gateway 8.8 
Improper access control on the NetScaler Management Interface CVE-2025-8424 NetScaler ADC & Gateway 8.7 

Technical Summary 

The NetScaler ADC and NetScaler Gateway appliances are affected by multiple critical vulnerabilities that pose significant risks ranging from Remote Code Execution (RCE) and Denial of Service (DoS) to improper access control.

These include memory overflow flaws in configurations such as VPN virtual servers, load balancing virtual servers using IPv6 or DBS IPv6 services, and misconfigurations involving PCoIP profiles. Additionally, the management interface is exposed due to weak access control mechanisms, which could allow unauthorized administrative access if attackers reach key management IP addresses like NSIP or SNIP. CISA has added one vulnerability (CVE-2025-7775) to its Known Exploited Vulnerabilities (KEV) Catalog and strongly urges organizations to apply patches immediately to prevent active exploitation. 

CVE ID System Affected  Vulnerability Details Impact 
CVE-2025-7775  NetScaler ADC & Gateway  A critical memory overflow vulnerability in NetScaler ADC and Gateway that can lead to Remote Code Execution or DoS when configured as a Gateway (e.g., VPN, ICA Proxy, CVPN, RDP Proxy), AAA virtual server, or LB virtual server using IPv6 or DBS IPv6 services including CR virtual servers of type HDX. Remote Code Execution or DoS  
CVE-2025-7776  NetScaler ADC & Gateway A memory overflow vulnerability under analysis, currently known to cause unpredictable system behavior and potential DoS when a PCoIP Profile is bound to a Gateway-configured NetScaler instance (VPN, ICA Proxy, CVPN, RDP Proxy), Erroneous behavior and DoS 
CVE-2025-8424 NetScaler ADC & Gateway An improper access control vulnerability on the NetScaler Management Interface, allowing unauthorized access when attackers can reach management IPs (NSIP, Cluster Management IP, local GSLB Site IP, or SNIP with Management Access), affecting NetScaler ADC and Gateway appliances. Unauthorized access 

Recommendations 

NetScaler ADC and NetScaler Gateway to install the relevant updated versions as soon as possible.  

  • NetScaler ADC and NetScaler Gateway 14.1-47.48 and later releases 
  • NetScaler ADC and NetScaler Gateway 13.1-59.22 and later releases of 13.1 
  • NetScaler ADC 13.1-FIPS and 13.1-NDcPP 13.1-37.241 and later releases of 13.1-FIPS and 13.1-NDcPP 
  • NetScaler ADC 12.1-FIPS and 12.1-NDcPP 12.1-55.330 and later releases of 12.1-FIPS and 12.1-NDcPP 

Here are some other recommendations below 

  • Monitor systems for unusual activity or unauthorized changes. 
  • Limit access to Citrix instances from untrusted networks. 
  • Use firewalls to block suspicious traffic targeting Citrix instances. 

Conclusion: 

Combined with additional high-severity vulnerabilities the overall threat landscape demands immediate attention. Organizations are strongly urged to apply the latest patches, restrict access to management interfaces and closely monitor for signs of compromise. Delayed action could result in significant operational and security impacts. 

The active exploitation of CVE-2025-7775 highlights a critical security threat affecting multiple NetScaler ADC and Gateway instances globally. This zero-day confirmed exploitation in the wild poses a severe risk of Remote Code Execution and service disruption.

References: 

  

Security Advisory

CitrixBleed 2: Critical CVE-2025-5777 Vulnerability Under Active Exploitation with Public PoC Available

Summary ; A critical vulnerability identified as CVE-2025-5777 has been discovered in Citrix NetScaler ADC and NetScaler Gateway products configured as Gateway or AAA virtual servers.

The Citrix NetScaler is a networking gadget that delivers application access across distributed enterprise environments.

Originally developed to optimize traffic and improve the performance of web applications, NetScaler has evolved into a comprehensive solution for load balancing, SSL offloading, web application firewalling (WAF), secure remote access, and gateway functionalities such as VPN and ICA proxy for Citrix Virtual Apps and Desktops.

OEM Citrix 
Severity Critical 
CVSS Score 9.3 
CVEs CVE-2025-5777 
POC Available Yes 
Actively Exploited Yes 
Exploited in Wild Yes 
Advisory Version 1.0 

Overview 

This out-of-bounds read flaw enables unauthenticated attackers to leak sensitive memory content, such as session tokens, by sending crafted HTTP POST requests. 

The vulnerability is actively exploited in the wild, with public PoC exploits and scanning tools available. Citrix has released patches, and urgent remediation is strongly recommended. 

Vulnerability Name CVE ID Product Affected Severity Fixed Version 
​ Out-of-bounds read vulnerability  CVE-2025-5777 NetScaler ADC & Gateway  Critical  14.1-43.56,   13.1-58.32, 13.1-FIPS/NDcPP 13.1 37.235, 12.1-FIPS 12.1-55.328 

Technical Summary 

CVE-2025-5777 arises from improper input validation during login requests on affected NetScaler devices. An attacker can exploit the flaw by submitting a malformed authentication request (eg. missing an equal sign in a POST login parameter). This leads the system to read uninitialized memory and leak up to 127 bytes of sensitive data. 

Attackers can extract session tokens and bypass multi-factor authentication (MFA) to hijack legitimate user sessions. 

CVE ID System Affected  Vulnerability Details Impact 
 CVE-2025-5777 NetScaler ADC & Gateway 14.1 < 14.1-43.56 13.1 < 13.1-58.32 13.1-FIPS/NDcPP < 13.1-37.235 12.1-FIPS < 12.1-55.328 EOL: 12.1, 13.0. Insufficient input validation allows attackers to trigger a memory leak via malformed authentication requests. Session hijacking, MFA bypass, unauthorized access 

Proof of Concept (PoC): 

  • Execution Flow 

Attacker submits a malformed HTTP POST to: 

POST /p/u/doAuthentication.do HTTP/1.0 

Host: <NetScaler-IP> 

Content-Length: 5 

Connection: keep-alive 

login  

(Note: the ‘login’ parameter is included without an ‘=’ or value.) * 

  • Memory Leak Trigger 

Due to insufficient input validation, the backend neither initializes nor validates the ‘login’ field. This causes up to 127 bytes of uninitialized stack memory to be included in the XML response ‘<InitialValue>’ tag potentially containing session tokens or sensitive internal data.  

    Source: horizon3 

Remediation: 

  • Immediate Action: Upgrade to the latest fixed versions:  – NetScaler ADC & Gateway 14.1-43.56 or later 
    – NetScaler ADC & Gateway 13.1-58.32 or later 
    – NetScaler ADC 13.1-FIPS/NDcPP 13.1-37.235 or later 
     – NetScaler ADC 12.1-FIPS 12.1-55.328 or later 
     – EOL versions (12.1, 13.0) must be upgraded to supported releases. 

Recommendations: 

  • Session Invalidation: After patching, terminate all active ICA and PCoIP sessions using: 
      kill icaconnection -all 
      kill pcoipConnection -all. 
  • Audit: Review authentication and session logs for suspicious activity, including repeated POST requests and session reuse across unexpected IPs. 
  • Upgrade Legacy Systems: Migrate EOL devices to supported versions as they will not receive security fixes. 

Conclusion: 
CVE-2025-5777 (CitrixBleed 2) represents a critical memory leak vulnerability that is being actively exploited, with working public exploits widely circulated.

Attackers can extract session tokens and take over sessions even with MFA in place. Shodan scans reveal over 50,000 exposed NetScaler instances, with more than 1,200 unpatched as of late June 2025 

Given its severity, public exploitation, and impact, organizations must act immediately to patch vulnerable systems, revoke active sessions, and migrate away from unsupported versions.

This vulnerability echoes the risks of the original CitrixBleed, emphasizing the importance of proactive defense in depth. 

References: 

Hashtags 

#Infosec #CyberSecurity #Critix #NetScaler #SecurityAdvisory #Vulnerabilitymanagement # Patch Management #CISO #CXO #Intrucept  

Security Advisory

Citrix NetScaler ADC/Gateway Vulnerability Exploited in the Wild (CVE-2025-6543) 

Summary : Security Advisory;

Citrix is warning that a vulnerability in NetScaler appliances tracked as CVE-2025-6543 is being actively exploited in the wild, causing devices to enter a denial of service condition.

The flaw impacts NetScaler ADC and NetScaler Gateway versions 14.1 before 14.1-47.46, 13.1 before 13.1-59.19, and NetScaler ADC 13.1-FIPS and NDcPP before 13.1-37.236-FIPS and NDcPP.

OEM Citrix 
Severity Critical 
CVSS Score 9.2 
CVEs CVE-2025-6543 
POC Available No 
Actively Exploited Yes 
Exploited in Wild Yes 
Advisory Version 1.0 

Overview 

A critical memory overflow vulnerability, CVE-2025-6543, has been discovered in NetScaler ADC and NetScaler Gateway products, potentially leading to denial-of-service and unintended control flow. The issue affects deployments configured as Gateway services. Active exploitation in the wild has been reported. 

Vulnerability Name CVE ID Product Affected Severity Fixed Version 
​Memory overflow vulnerability  CVE-2025-6543 NetScaler ADC and NetScaler Gateway  Critical  14.1-47.46 / 13.1-59.19 / 13.1-37.236 

Technical Summary 

CVE-2025-6543 is a memory overflow vulnerability in NetScaler ADC and Gateway products that can result in denial-of-service (DoS) or arbitrary control flow, particularly when the system is configured as a Gateway or AAA virtual server.

The flaw stems from improper restriction of operations within memory buffer bounds (CWE-119). This vulnerability has been exploited in real-world attacks. 

CVE ID System Affected  Vulnerability Details Impact 
  CVE-2025-6543 NetScaler ADC & Gateway 14.1 before 14.1-47.46, 13.1 before 13.1-59.19 NetScaler ADC 13.1-FIPS and NDcPP before 13.1-37.236-FIPS and NDcPP Memory overflow due to improper memory boundary restrictions when configured as Gateway or AAA virtual servers  Denial-of-Service and Unintended control flow 

Remediation: 

  • Immediate Action: Affected customers are strongly advised to upgrade to the fixed versions: 
Product Version Recommended Fixed Build 
NetScaler ADC / Gateway 14.1 14.1-47.46 or later 
NetScaler ADC / Gateway 13.1 13.1-59.19 or later 
NetScaler ADC 13.1-FIPS / NDcPP 13.1-37.236 or later 

Note: Versions 12.1 and 13.0 are End-of-Life (EOL) and remain vulnerable. These should be replaced with supported, patched builds. 

Customers using FIPS or NDcPP variants should contact Citrix Support directly for access to the fixed builds. 

Conclusion: 
CVE-2025-6543 represents a highly critical risk to organizations utilizing NetScaler Gateway or ADC for secure access and application delivery.

Organizations still using outdated or end-of-life (EOL) versions are especially vulnerable and should prioritize upgrading to supported builds. 

This flaw follows a pattern of severe vulnerabilities affecting NetScaler products, including the recently disclosed CVE-2025-5777 (CVSS score: 9.3), which also posed a significant threat to enterprise infrastructure.

Together these issues highlight the urgent need for timely patching, continuous monitoring, and defense-in-depth strategies to safeguard critical network assets. 

With both flaws being critical bugs, administrators are advised to apply the latest patches from Citrix as soon as possible.

Companies should also monitor their NetScaler instances for unusual user sessions, abnormal behavior, and to review access controls.

References: 

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