Citrix Bleed Scare: How to Fortify Your Network Against CVE-2022-27518

The CVE-2022-27518 (also known as CVE-2023-4966 or Citrix Bleed) vulnerability in Citrix Application Delivery Controllers (ADC) and Gateway represents a significant security issue affecting a wide array of organizations globally. This critical security flaw has been actively exploited since at least August 2023 and can’t be fully remediated by simply applying the patch, making it a severe concern for business continuity and the security of sensitive data​​​​.

The scale of the problem
The vulnerability has been targeted by threat actors against government, technical, and legal organizations across the Americas, Europe, Africa, and the Asia-Pacific region, indicating a broad scale of potential impact​​.

Customers affected
Given the widespread use of Citrix products for application delivery within enterprises, the number of customers affected is potentially vast. Threat actors have been able to hijack existing authenticated sessions and bypass multifactor authentication (MFA), leading to full control over NetScaler environments​​.

Possibility of large data breach
The exploitation of the vulnerability leaves behind limited forensic evidence, which combined with the ability for lateral movement and credential theft, raises the possibility of significant data breaches. Attackers have been using this vulnerability to engage in network reconnaissance, stealing account credentials, and moving laterally across networks, which could lead to large-scale data breaches if not promptly and effectively addressed​​.

Critical services affected
Given that the ADCs and Gateways are used to control and manage application delivery, a range of critical services could be affected, including those that require high availability and security, such as healthcare systems, financial services, and government operations​​.

Business continuity issues
Organizations are warned that even after the patch is applied, active sessions may persist, allowing threat actors to continue to authenticate to resources. This persistent threat could lead to significant business continuity issues, as organizations may need to terminate all active sessions and conduct a full incident response to ensure the security of their systems​​.

Additional considerations

• Mandiant warns that simply patching the systems is not enough; a full incident response is required to address existing breaches.
• The lack of logging on the appliances makes investigating the exploitation challenging, requiring additional network traffic monitoring to determine if a device was exploited​​.
• Threat actors use a range of common administrative tools and novel backdoors, making detection difficult. Mandiant has released a Yara rule to detect one of the backdoors, FREE FIRE, on devices​​.
• The disclosure of a proof-of-concept (PoC) exploit on October 25 by AssetNote researchers demonstrates the ease of exploiting this vulnerability, potentially leading to increased attacks​​.

In conclusion, the CVE-2022-27518 vulnerability presents a critical challenge to organizations using Citrix ADC and Gateway products. The widespread and stealthy nature of the attacks, the difficulty in remediation, and the high stakes for businesses highlight the need for a comprehensive security response that goes beyond patching to include active monitoring, incident response, and potentially a review of network architecture and security practices.

by Morgan Phisher | HEAL Security