CVE-2008-1692 in Eterm
Summary
by MITRE
Eterm 0.9.4 opens a terminal window on :0 if -display is not specified and the DISPLAY environment variable is not set, which might allow local users to hijack X11 connections. NOTE: realistic attack scenarios require that the victim enters a command on the wrong machine.
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Analysis
by VulDB Data Team • 08/10/2019
The vulnerability identified as CVE-2008-1692 affects Eterm version 0.9.4, a terminal emulator application that fails to properly handle X11 display connections when specific environmental conditions are met. This flaw represents a classic privilege escalation and session hijacking vulnerability that exploits the default behavior of X11 windowing system connections. The vulnerability stems from the application's lack of proper validation when determining which display to connect to, creating a potential attack vector for local users who wish to gain unauthorized access to graphical sessions. When the -display command line argument is not provided and the DISPLAY environment variable is unset, Eterm defaults to connecting to display :0, which typically represents the local machine's primary graphical display.
The technical implementation of this vulnerability involves the application's connection handling mechanism within the X11 protocol framework. When Eterm initializes without explicit display parameters, it falls back to the default X11 display :0, which is commonly accessible to local users on Unix-like systems. This behavior creates an opportunity for attackers to manipulate the environment or exploit the default connection logic to establish unauthorized access to the local graphical session. The vulnerability specifically relates to improper input validation and default configuration handling within the X11 subsystem integration, where the application does not properly verify or sanitize the display connection parameters before establishing the graphical session. This type of flaw maps directly to CWE-284, which addresses improper access control, and CWE-352, which covers cross-site request forgery, as the vulnerability enables unauthorized access to graphical sessions through default configuration settings.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it enables potential session hijacking and unauthorized access to graphical user interfaces. An attacker can exploit this weakness to gain access to graphical sessions that would otherwise be protected by proper authentication mechanisms. The attack requires a specific condition where the victim performs actions on the wrong machine, indicating that social engineering or misconfiguration may be necessary to fully exploit the vulnerability. This makes the attack more complex but still potentially viable in environments where users may not be fully aware of their current system context or where local privilege escalation opportunities exist. The vulnerability essentially allows for unauthorized access to the local X11 display server, potentially enabling attackers to observe or control graphical sessions, execute commands with the privileges of the logged-in user, or perform other malicious activities within the graphical environment.
Mitigation strategies for this vulnerability involve multiple layers of protection that address both the immediate application-level flaw and broader system security considerations. System administrators should ensure that Eterm is properly configured with explicit display parameters or that the DISPLAY environment variable is correctly set to prevent the default fallback behavior. The recommended approach includes implementing proper environment variable validation and ensuring that applications do not automatically connect to display :0 without explicit user authorization. Additionally, system hardening measures such as restricting local access to X11 servers, implementing proper access controls for graphical sessions, and employing proper privilege separation techniques can significantly reduce the attack surface. This vulnerability also highlights the importance of proper application security testing, particularly around default configuration handling and environmental parameter validation, as outlined in the ATT&CK framework under T1068 for exploit for privilege escalation and T1548 for abuse of privileges. Organizations should also consider implementing monitoring and alerting for unusual X11 connection patterns that may indicate exploitation attempts.