CVE-2000-1060 in XFce
Summary
by MITRE
The default configuration of XFCE 3.5.1 bypasses the Xauthority access control mechanism with an "xhost + localhost" command in the xinitrc program, which allows local users to sniff X Windows traffic and gain privileges.
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Analysis
by VulDB Data Team • 05/28/2018
The vulnerability described in CVE-2000-1060 represents a critical security flaw in the default configuration of XFCE desktop environment version 3.5.1. This issue stems from the improper handling of X Windows access control mechanisms within the xinitrc initialization script, creating a significant attack surface that compromises the security posture of affected systems. The vulnerability specifically targets the Xauthority access control system that is fundamental to X Window protocol security, which is designed to prevent unauthorized access to graphical sessions and protect against man-in-the-middle attacks.
The technical flaw manifests through the execution of the "xhost + localhost" command within the xinitrc program, which effectively disables access control for local connections to the X server. This command removes the security restrictions that normally require authentication tokens or specific access control entries to connect to the X server. According to CWE-284, this represents an improper access control vulnerability where the system fails to properly enforce access restrictions, allowing unauthorized entities to gain access to protected resources. The xhost command's behavior of adding localhost to the access control list creates a backdoor that bypasses the Xauthority mechanism, which is the standard method for managing access to X server resources in Unix-like systems.
The operational impact of this vulnerability is severe as it enables local users to perform packet sniffing on X Windows traffic, potentially capturing sensitive information transmitted between applications and the X server. This capability allows attackers to observe graphical sessions, capture keystrokes, and potentially extract authentication credentials or other sensitive data. The vulnerability aligns with ATT&CK technique T1056.001 for input injection and T1046 for network service scanning, as the compromised access control allows for reconnaissance and data interception activities. Additionally, this flaw can serve as a stepping stone for privilege escalation attacks, as captured X traffic might contain authentication tokens or other credentials that could be exploited to gain higher privileges within the system.
The security implications extend beyond simple traffic interception, as this vulnerability demonstrates poor security practices in desktop environment configuration. The default installation of XFCE 3.5.1 included a configuration that explicitly weakened security controls, creating an environment where local users could exploit the system's graphical interface access controls. This vulnerability highlights the importance of secure default configurations and the principle of least privilege in system design. Organizations using XFCE or similar desktop environments should implement proper access control measures, including disabling the xhost command in initialization scripts and ensuring that Xauthority files are properly configured with appropriate permissions. System administrators should also consider implementing additional network security measures such as X11 forwarding restrictions and monitoring for unauthorized access attempts to X server resources. The vulnerability serves as a reminder that desktop environments must balance usability with security, and default configurations should never compromise system integrity for convenience.