CVE-2008-1293 in Linux Terminal Server Project
Summary
by MITRE
ldm in Linux Terminal Server Project (LTSP) 0.99 and 2 passes the -ac option to the X server on each LTSP client, which allows remote attackers to connect to this server via TCP port 6006 (aka display :6).
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Analysis
by VulDB Data Team • 08/10/2019
The vulnerability identified as CVE-2008-1293 resides within the Linux Terminal Server Project LTSP implementation, specifically affecting versions 0.99 and 2.0. This flaw manifests in the ldm component which is responsible for managing display connections in LTSP environments. The core issue stems from improper handling of X server arguments where the -ac option is passed to the X server on each client machine. This configuration directive disables access control for the X server, effectively removing the security mechanism that would normally prevent unauthorized connections to the display server.
The technical exploitation of this vulnerability occurs through the exposure of TCP port 6006, which corresponds to X11 display :6. When the -ac option is enabled, it removes the X server's built-in access control restrictions, allowing any remote attacker to establish a connection to the display server without authentication. This represents a fundamental breach of the X Window System security model, which is designed to prevent unauthorized access to graphical displays. The vulnerability creates a direct pathway for remote attackers to gain access to the graphical interface of LTSP clients, potentially enabling them to execute arbitrary commands, capture keystrokes, or perform screen scraping operations.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it fundamentally undermines the security architecture of LTSP deployments. Organizations relying on LTSP for terminal server implementations face significant risks including potential data exfiltration, session hijacking, and unauthorized system control. The vulnerability affects the confidentiality, integrity, and availability of the affected systems, particularly in environments where LTSP is used for thin client deployments. Security professionals should recognize this as a critical issue that can be exploited without authentication, making it particularly dangerous in network environments where the affected systems are accessible from external networks.
This vulnerability aligns with CWE-284, which addresses improper access control in software systems, and can be mapped to ATT&CK technique T1074.001 for data staging through the potential for screen capture and data exfiltration. The flaw demonstrates a classic case of insecure default configurations where security mechanisms are disabled through command-line arguments without proper consideration of the network exposure. Mitigation strategies should focus on removing the -ac option from the X server invocation in LTSP configurations, implementing proper network segmentation to isolate LTSP environments, and ensuring that TCP port 6006 is not exposed to untrusted networks. Additionally, organizations should consider implementing network access controls and firewall rules to restrict access to the X server ports, while also reviewing and updating their LTSP configurations to disable access control in a secure manner. The vulnerability highlights the importance of understanding the security implications of command-line options in server applications and the necessity of proper security auditing of system configurations in terminal server environments.