CVE-2000-1059 in Mandrake Linux
Summary
by MITRE
The default configuration of the Xsession file in Mandrake Linux 7.1 and 7.0 bypasses the Xauthority access control mechanism with an "xhost + localhost" command, which allows local users to sniff X Windows events and gain privileges.
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Analysis
by VulDB Data Team • 05/01/2019
The vulnerability described in CVE-2000-1059 represents a critical security flaw in the X Window System authentication mechanism within Mandrake Linux versions 7.0 and 7.1. This issue stems from the default configuration of the Xsession file which executes an "xhost + localhost" command during system initialization. The Xauthority mechanism serves as a fundamental security component in the X Window System, designed to control access to X server resources by maintaining a list of clients authorized to connect and interact with the display server. When the xhost command is executed with the localhost parameter, it effectively disables access control for local connections, creating an exploitable condition that undermines the core security model of the X Window System.
The technical flaw in this vulnerability resides in the improper handling of X11 access control permissions within the system's default desktop environment configuration. The xhost + localhost command removes the Xauthority restrictions for local connections, allowing any local process running on the same machine to potentially intercept X11 events and communications. This creates a privilege escalation vector where local users can capture sensitive information transmitted through the X Window System, including keyboard input, window contents, and other graphical interface communications. The vulnerability directly maps to CWE-284, which addresses improper access control in system components, specifically targeting the X Window System's authentication mechanisms. Additionally, this flaw aligns with ATT&CK technique T1056.001 which covers input injection attacks, as malicious processes can intercept and manipulate X11 events to gain unauthorized access to graphical sessions.
The operational impact of this vulnerability extends beyond simple information disclosure to include potential privilege escalation and session hijacking capabilities. Local users can exploit this condition to monitor and capture X11 events, which may contain sensitive data such as passwords entered through graphical interfaces, confidential document contents, and other protected information. The vulnerability creates an attack surface that allows adversaries to perform reconnaissance activities against running graphical sessions, potentially leading to credential theft and unauthorized access to user accounts. The security implications are particularly severe in multi-user environments where one local user could potentially monitor or manipulate the graphical sessions of other users on the same system. This flaw essentially provides a backdoor mechanism that bypasses the intended security boundaries of the X Window System, enabling unauthorized access to graphical user interfaces and the sensitive data they handle.
Mitigation strategies for this vulnerability must address both the immediate configuration issue and broader system security practices. The primary remediation involves modifying the Xsession configuration to remove or properly secure the xhost command execution, ensuring that Xauthority mechanisms remain intact for local connections. System administrators should implement proper access control lists and avoid blanket permissions for localhost connections. The recommended approach includes configuring X server to use proper authentication mechanisms such as Xauthority files and avoiding commands that disable access control. Organizations should also consider implementing additional security measures including regular system audits to detect unauthorized X11 access control modifications, monitoring for suspicious X11 activity, and ensuring that all system components maintain proper authentication boundaries. This vulnerability underscores the importance of secure default configurations in operating systems and highlights the critical need for proper access control implementation in graphical user interface systems. The flaw demonstrates how seemingly benign configuration settings can create significant security weaknesses when they bypass fundamental security mechanisms.