CVE-2007-3920 in Compiz
Summary
by MITRE
GNOME screensaver 2.20 in Ubuntu 7.10, when used with Compiz, does not properly reserve input focus, which allows attackers with physical access to take control of the session after entering an Alt-Tab sequence, a related issue to CVE-2007-3069.
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Analysis
by VulDB Data Team • 07/30/2019
The vulnerability identified as CVE-2007-3920 affects the GNOME screensaver version 2.20 implementation within Ubuntu 7.10 operating system, specifically when integrated with the Compiz window manager. This security flaw represents a critical session hijacking vulnerability that exploits the improper handling of input focus mechanisms within the desktop environment. The issue manifests when an attacker with physical access to a system can exploit the screensaver's failure to properly manage focus reservation, creating an opportunity for unauthorized session control after executing an Alt-Tab sequence.
The technical root cause of this vulnerability lies in the screensaver component's inadequate implementation of input focus management protocols. When GNOME screensaver operates in conjunction with Compiz, the system fails to maintain proper focus reservation during screensaver activation, allowing the window manager to relinquish control in a manner that can be exploited. This flaw specifically relates to the improper handling of focus events and the failure to establish secure focus states that would prevent unauthorized input interception. The vulnerability is categorized under CWE-284 Access Control, as it represents a failure in proper access control mechanisms that should prevent unauthorized users from gaining control over active sessions.
The operational impact of this vulnerability is particularly severe given the physical access requirement and the specific interaction with Compiz window manager. An attacker with physical access to a system can execute an Alt-Tab sequence to transition between applications, then exploit the screensaver's focus handling weakness to regain control of the session. This creates a window of opportunity where the attacker can potentially access sensitive information, execute commands, or perform other malicious activities within the active user session. The vulnerability essentially undermines the fundamental security assumption that a screensaver should provide protection against unauthorized access, particularly when the system is in a locked state.
This vulnerability aligns with several ATT&CK techniques including T1078 Valid Accounts and T1547 Boot or Logon Autostart Execution, as it exploits legitimate session management mechanisms to gain unauthorized access. The issue demonstrates a clear failure in the principle of least privilege and proper session management within desktop environments. The relationship to CVE-2007-3069 indicates this represents a broader class of vulnerabilities affecting screensaver implementations in graphical desktop environments, where focus management and input handling are inadequately secured. Organizations using affected versions of Ubuntu with Compiz should consider immediate remediation through system updates, focus management policy changes, or alternative window manager configurations to prevent exploitation of this session hijacking vulnerability.
The remediation approach should prioritize system updates to address the specific screensaver implementation flaw, while also implementing additional security controls such as disabling unnecessary window manager features, enforcing proper session lock mechanisms, and ensuring that physical security measures are maintained. Organizations should also consider implementing monitoring for unusual Alt-Tab sequences or focus changes that might indicate exploitation attempts. The vulnerability underscores the importance of proper focus management in desktop security implementations and highlights the need for comprehensive testing of graphical user interface components for security weaknesses that could be exploited through physical access scenarios.