CVE-2019-13608 Scanner

Citrix StoreFront Server is an integral component used extensively in virtual application and desktop delivery solutions. Deployed by IT service providers, it manages the authentication and aggregation of virtual applications delivered from Citrix Virtual Apps and Desktops. Utilized by organizations for secure access to virtual environments, StoreFront Server is essential for maintaining consistent, high-performance end-user experiences across diverse endpoints. The server is part of the suite that supports remote work by providing secure access to enterprise applications and data. Its built-in features enable seamless integration with existing corporate environments, enhancing the utility and flexibility of Citrix offerings. As such, the security of Citrix StoreFront Server is paramount for protecting sensitive enterprise data and ensuring business continuity.

XML External Entity (XXE) vulnerabilities arise when XML input containing a reference to an external entity is processed by a parser or processor.. This vulnerability can be exploited by attackers to read local files, send HTTP requests, or perform denial of service attacks among other malicious activities. The issue typically occurs due to misconfiguration or incorrect handling of XML data within an application. It allows attackers to access sensitive data or potentially execute arbitrary commands. Exploiting XXE can lead to significant security breaches, compromising organizational data, impeding service functionality, and affecting system reliability. In systems like Citrix StoreFront Server, the exploitation of XXE vulnerabilities poses grave threats due to the critical nature of the application's role in IT infrastructure.

The XML External Entity (XXE) vulnerability in Citrix StoreFront Server can be exploited through certain XML-based communication endpoints that fail to properly validate input data. A notable technical detail involves exploiting malformed XML payloads, specifically crafted to reference an external resource, which the XML parser erroneously attempts to retrieve. Attackers leverage this flaw by manipulating crafted data within the XML message to target resources on the same server, other servers, or even external malicious sites. The vulnerable endpoint, typically involved in processing authentication or configuration payloads, can become a conduit for requests that the server unwittingly executes. This exploitation path underscores the importance of proper input validation and adherence to best practices in XML parsing and processing. Without robust safeguards, attackers can exploit these weaknesses to extract sensitive files, undermine application integrity, or escalate their access within the network.

When malicious actors exploit an XML External Entity (XXE) vulnerability in Citrix StoreFront Server, several detrimental outcomes are possible. By reading arbitrary files, attackers might gain access to sensitive configuration information, credentials, or data. This data breach could allow further exploits within the compromised environment or facilitate cross-environment attacks if the server interacts with other systems. Server-side request forgery attacks could be orchestrated, manipulating the server to interact with external malicious resources. Additionally, service availability could be impacted, particularly if XXE is leveraged to execute denial of service attacks, disrupting legitimate user access. Ultimately, the exploitation of XXE vulnerabilities threatens data confidentiality, system integrity, and the availability of critical services, underscoring the need for rigorous security measures.

REFERENCES

• https://www.exploit-db.com/exploits/47561
• https://support.citrix.com/support-home/kbsearch/article?articleNumber=CTX251988
• https://nvd.nist.gov/vuln/detail/CVE-2019-13608