CVE-2006-6105 in Display Manager
Summary
by MITRE
Format string vulnerability in the host chooser window (gdmchooser) in GNOME Foundation Display Manager (gdm) allows local users to execute arbitrary code via format string specifiers in a hostname, which are used in an error dialog.
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Analysis
by VulDB Data Team • 07/14/2019
The vulnerability identified as CVE-2006-6105 represents a critical format string flaw within the GNOME Display Manager's host chooser component known as gdmchooser. This issue exists within the broader GNOME Foundation Display Manager ecosystem, which serves as the primary graphical login interface for GNOME desktop environments and manages user authentication processes. The vulnerability specifically manifests in the error dialog handling mechanism where hostname input is processed without proper sanitization, creating an exploitable condition that can be leveraged by local attackers to execute arbitrary code on affected systems. The flaw resides in the improper handling of user-supplied input within the display manager's graphical interface components, particularly when processing hostnames entered by users in the host selection window.
The technical exploitation of this vulnerability occurs through the manipulation of format string specifiers within hostname values entered by local users. When the gdmchooser component processes these hostnames and subsequently displays them in error dialogs, it fails to properly escape or validate the input before using it in printf-style formatting operations. This creates a classic format string vulnerability where attackers can inject malicious format specifiers such as %n, %s, or %x that can lead to memory corruption, information disclosure, or arbitrary code execution. The vulnerability is classified under CWE-134, which specifically addresses the use of untrusted data in format string operations, making it a well-documented and dangerous class of vulnerability in software security. Attackers can leverage this flaw to overwrite memory locations, execute shellcode, or gain elevated privileges, particularly when the display manager runs with sufficient permissions to affect system operations.
The operational impact of CVE-2006-6105 extends beyond simple code execution as it represents a privilege escalation vector within the display manager context. Since gdm typically runs with elevated privileges to manage system authentication and user sessions, successful exploitation can result in complete system compromise. Local users who can access the host chooser interface can leverage this vulnerability to execute malicious code with the privileges of the display manager process, potentially leading to unauthorized system access, data exfiltration, or further exploitation of the compromised system. The vulnerability affects all systems running affected versions of GNOME Display Manager where the gdmchooser component is accessible, making it particularly dangerous in multi-user environments where local access is possible. This flaw directly aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation', and T1059, covering 'Command and Scripting Interpreter', as attackers can use the vulnerability to execute arbitrary commands through the format string exploitation.
Mitigation strategies for CVE-2006-6105 must address both the immediate vulnerability and broader security practices within the GNOME ecosystem. The primary remediation involves applying security patches from GNOME Foundation that properly sanitize hostname inputs before using them in format string operations, ensuring that all user-supplied data is escaped or validated before processing. System administrators should implement access controls to limit local user access to the gdmchooser interface when possible, as well as deploy application whitelisting policies that restrict execution of potentially malicious code. Additionally, organizations should consider implementing intrusion detection systems to monitor for exploitation attempts and establish regular security audits of display manager configurations. The vulnerability demonstrates the importance of input validation and proper error handling in graphical user interfaces, as highlighted by industry best practices in secure coding standards and security frameworks that emphasize the need for robust sanitization of all user inputs in security-critical applications.