CVE-2012-1620 in slock
Summary
by MITRE
slock 0.9 does not properly handle the XRaiseWindow event when the screen is locked, which might allow physically proximate attackers to obtain sensitive information by pressing a button, which reveals the desktop and active windows.
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Analysis
by VulDB Data Team • 02/18/2019
The vulnerability identified as CVE-2012-1620 affects slock version 0.9, a simple screen locker utility commonly used in X Window System environments. This flaw represents a critical security issue within the window management and screen locking mechanisms of Unix-like operating systems. The vulnerability stems from improper handling of the XRaiseWindow X11 protocol event when the screen is locked, creating a window management race condition that undermines the fundamental security assumptions of screen locking mechanisms.
The technical flaw manifests when slock fails to properly intercept or process the XRaiseWindow event that occurs when windows are raised to the foreground. This event typically triggers when applications attempt to bring windows to the front of the display stack, which can happen through various user interactions or system events. When slock does not adequately handle this specific X11 event during the locked state, it creates an unintended pathway for attackers to bypass the screen lock protection. The vulnerability specifically allows attackers to gain access to the desktop environment and active windows without proper authentication, essentially undermining the core purpose of screen locking.
The operational impact of this vulnerability is particularly concerning for physically proximate attackers who may be positioned near a locked workstation. Such attackers can exploit this flaw by pressing specific buttons or triggering certain system events that cause windows to be raised, thereby revealing the desktop contents and active applications. This exposure can lead to unauthorized access to sensitive information, including open applications, documents, email contents, and other confidential data that may be visible on the screen. The vulnerability essentially creates a backdoor that allows attackers to circumvent screen lock security measures without requiring any sophisticated attack techniques or network access.
This vulnerability aligns with CWE-284, which addresses inadequate access control mechanisms, and specifically relates to improper handling of window management events in security-critical applications. The flaw demonstrates a classic example of how seemingly minor implementation details in security software can create significant vulnerabilities. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation and credential access techniques, as attackers can leverage this weakness to obtain unauthorized access to system resources without proper authentication. The vulnerability also reflects poor input validation and event handling practices in security-sensitive software components.
Mitigation strategies for this vulnerability require immediate patching of slock to properly handle XRaiseWindow events during screen lock states. System administrators should ensure that all instances of slock are updated to versions that address this specific event handling issue. Additionally, organizations should consider implementing additional security measures such as automatic screen locking after periods of inactivity, proper physical security controls, and monitoring for unusual window management events. The vulnerability highlights the importance of thorough testing of security software under various event conditions and demonstrates the critical need for proper event handling in security-critical applications. Organizations should also review their screen locking configurations and ensure that multiple layers of security are implemented to protect against similar vulnerabilities in other system components.