CVE-2000-0244 in MetaFrame
Summary
by MITRE
The Citrix ICA (Independent Computing Architecture) protocol uses weak encryption (XOR) for user authentication.
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Analysis
by VulDB Data Team • 12/23/2024
The Citrix ICA protocol vulnerability described in CVE-2000-0244 represents a critical cryptographic weakness that fundamentally undermines the security of remote desktop sessions. This vulnerability specifically targets the authentication mechanism within the ICA protocol, which was widely adopted for remote access solutions in enterprise environments throughout the late 1990s and early 2000s. The flaw stems from the implementation of weak XOR encryption for user credentials during the authentication process, creating a significant attack surface that adversaries could exploit to gain unauthorized access to systems.
The technical implementation of this vulnerability involves the use of simple XOR operations for encrypting authentication tokens and user credentials transmitted between client and server components of the Citrix environment. This encryption method provides minimal security guarantees and can be easily reversed through cryptographic analysis, particularly when attackers have access to multiple authentication exchanges. The XOR encryption algorithm lacks the complexity and randomness required for modern cryptographic standards, making it susceptible to pattern analysis and brute force attacks. This weakness is classified under CWE-327, which specifically addresses the use of weak cryptographic algorithms, and aligns with ATT&CK technique T1550.001 for use of stolen credentials and T1071.004 for application layer protocol.
The operational impact of this vulnerability extends far beyond simple credential theft, as it enables attackers to establish persistent access to enterprise networks through compromised Citrix servers. Organizations relying on ICA protocol implementations for remote desktop services faced significant risks including unauthorized data access, privilege escalation, and potential lateral movement within their network infrastructure. The vulnerability was particularly dangerous because it affected the core authentication mechanism rather than just data transmission, meaning that even if other security controls were in place, successful exploitation could bypass them entirely. This weakness was especially problematic in environments where Citrix servers served as primary gateways for remote access, creating single points of failure that could compromise entire network perimeters.
Mitigation strategies for this vulnerability required immediate implementation of protocol-level fixes and architectural changes to prevent exploitation. Organizations needed to upgrade their Citrix server implementations to versions that employed stronger encryption algorithms, typically transitioning from XOR-based mechanisms to more robust cryptographic implementations such as those based on RC4 or AES. Network segmentation and additional authentication layers became essential defensive measures, as the vulnerability could not be fully resolved through simple configuration changes. Security teams were advised to conduct comprehensive audits of their Citrix implementations and implement monitoring solutions to detect potential exploitation attempts. The vulnerability highlighted the importance of proper cryptographic implementation in enterprise protocols and contributed to industry-wide awareness of the risks associated with weak encryption in authentication systems, ultimately influencing the development of more secure remote access protocols and standards.