Uncovering CVE-2023-3519: Critical Remote Code Execution Vulnerability in Citrix ADC

Critical vulnerabilities were discovered in Citrix ADC’s (formerly known as NetScaler Gateway) widely used enterprise products for secure application delivery and VPN (virtual private networks) connectivity. These products are used extensively across the world, especially within critical infrastructure organizations – hence, these vulnerabilities are critical to mitigate the risk of remote code execution (RCE).

Among the vulnerabilities discovered, the most concerning one, CVE-2023-3519, with a CVSS Score 9.8, allowed unauthenticated RCE, potentially affecting over 15,000 servers worldwide. The organizations impacted are primarily concentrated in the United States and Germany.

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) promptly issued an advisory on July 18, 2023, emphasizing the need for affected organizations to take immediate action to secure their systems from potential exploitation.
Accompanying CVE-2023-3519, Citrix ADC also resolved two other critical vulnerabilities. CVE-2023-3466 (CVSS score: 8.3) involved an improper input validation leading to a reflected XSS attack, while CVE-2023-3467 (CVSS score: 8.0) could result in improper privilege management and potential privilege q  escalation to the root administrator (nsroot). Prompt resolution of these issues was crucial to uphold the security of the systems.

Impact of Citrix CVE-2023-3519

The vulnerability was caused by a problem in how Citrix ADC manages XML requests. Hackers could exploit this flaw by sending specially crafted XML requests to a vulnerable appliance, enabling them to execute arbitrary code on the system.
“Exploits of CVE-2023-3519 on unmitigated appliances have been observed. Cloud Software Group strongly urges affected customers of NetScaler ADC and NetScaler Gateway to install the relevant updated versions as soon as possible.” reads the report published by Citrix.
Once exploited, threat actors can gain complete control over the compromised appliance, potentially leading to data theft, malware installation, or operational disruptions.

The impact of CVE-2023-3519 cannot be understated. With unauthenticated remote code execution (RCE) capabilities, hackers can wreak havoc on targeted systems and potentially compromise sensitive data within an organization’s network. However, taking the prompt action recommended by Citrix can support affected organizations in reducing these risks and stopping preventable breaches.

The following versions of Citrix ADC formerly known as NetScaler Gateway were confirmed to be affected by CVE-2023-3519:

• NetScaler ADC and NetScaler Gateway 13.1 before 13.1-49.13
• NetScaler ADC and NetScaler Gateway 13.0 before 13.0-91.13
• NetScaler ADC and NetScaler Gateway version 12.1
• NetScaler ADC 13.1-FIPS before 13.1-37.159
• NetScaler ADC 12.1-FIPS before 12.1-55.297
• NetScaler ADC 12.1-NDcPP before 12.1-55.297

These CVEs underscore the significance of solutions such as endpoint detection and response (EDR) in safeguarding critical infrastructure. Deploying EDR technologies to monitor firewalls, IoT devices, hypervisors, and VPNs, can bolster an organization’s defense-in-depth layers to stop sophisticated attack paths.

Mitigation of CVE-2023-3519

Citrix swiftly responded by releasing security updates to address the vulnerability. All organizations using Citrix ADC were strongly advised to install these updates immediately. Furthermore, the CISA issued additional guidance to help organizations bolster their security measures and protect their systems against potential exploitation.

The discovery of CVE-2023-3519 highlighted the importance of proactive vulnerability management practices and the rapid deployment of security patches. Timely updates are critical to prevent threat actors from exploiting known vulnerabilities. Organizations relying on enterprise-facing products like Citrix ADC should establish robust vulnerability management programs to stay ahead of potential threats.

Important! It’s crucial to note that there are no available patches for Citrix ADC (NetScaler) version 12.1 or older. As these systems have reached their End-of-Life (EOL), they will no longer receive the necessary fixes. In such cases, updating to the latest versions, specifically 13.0 or 13.1, is highly recommended to ensure the vulnerability is addressed.

Shield your Organization with Proactive Vulnerability Identification

Navigating today’s complex cybersecurity landscape can be challenging, especially when critical vulnerabilities like CVE-2023-3519 present timely risks, such as remote code execution, that require rapid remediation. When vulnerability identification and patch management are strengthened, organizations can quickly take action to safeguard their sensitive, regulated data, when a new critical CVE is issued. With remediation workflows and integrated ticketing systems in place, DevSecOps teams can work together with Security Operations to ensure the rhythm of the business is not disrupted due to an unpatched CVE.

With BreachLock, security leaders can access a comprehensive penetration testing platform, vulnerability scanning services, and a dedicated team of security experts. This empowers your organization to take control and oversee the remediation process for vulnerabilities, including those affecting Citrix ADC, using the BreachLock client portal and penetration testing services.

Your organization can benefit from exclusive access to a team of dedicated experts committed to securing your digital assets. BreachLock’s in-house certified penetration testing and red teaming experts are relentless in fortifying your defences and are ready to start your test within one business day. By partnering with BreachLock, you can confidently manage your organization’s penetration testing process and secure your full-stack IT systems proactively. Schedule a discovery call with BreachLock today.