CVE-2008-0887 in screensaver
Summary
by MITRE
gnome-screensaver before 2.22.1, when a remote authentication server is enabled, crashes upon an unlock attempt during a network outage, which allows physically proximate attackers to gain access to the locked session, a related issue to CVE-2007-1859.
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Analysis
by VulDB Data Team • 06/01/2025
The vulnerability described in CVE-2008-0887 affects the gnome-screensaver component in versions prior to 2.22.1, specifically when remote authentication servers are configured for use. This issue represents a critical security flaw that undermines the fundamental purpose of screen locking mechanisms in graphical desktop environments. The vulnerability manifests when users attempt to unlock their systems during network connectivity disruptions, creating a window of opportunity for unauthorized access.
The technical flaw stems from inadequate error handling within the gnome-screensaver daemon when it attempts to communicate with remote authentication services. During network outages, the authentication process fails, causing the screensaver to crash or become unresponsive rather than gracefully handling the failure state. This crash condition effectively removes the security barrier that should prevent unauthorized access to locked sessions. The system's inability to properly manage authentication failures during network disruptions creates a race condition where the session remains accessible to attackers who are physically present at the machine.
From an operational perspective, this vulnerability exposes systems to what is commonly known as a "physical proximity attack" vector. An attacker who can gain physical access to a locked workstation during network outages can exploit this flaw to bypass the screen locking mechanism entirely. The impact extends beyond simple unauthorized access to potentially sensitive data, as attackers can perform actions with the privileges of the logged-in user. This vulnerability directly relates to the broader category of authentication bypass issues that have been classified under CWE-284, which deals with inadequate access control mechanisms.
The security implications of this vulnerability align with several ATT&CK framework techniques including T1547.001 for hijacking legitimate processes and T1078 for valid accounts. The crash condition essentially provides a path for privilege escalation through session hijacking, as the system fails to maintain proper session state during authentication failures. This behavior particularly affects enterprise environments where network connectivity can be intermittent, making the vulnerability more exploitable in real-world scenarios. Organizations using gnome-screensaver in conjunction with remote authentication services face significant risk when operating with vulnerable versions.
Mitigation strategies should focus on immediate patching of affected gnome-screensaver installations to version 2.22.1 or later, which contains the necessary fixes for proper error handling during network outages. System administrators should also implement network monitoring to detect and alert on authentication service failures that could lead to similar vulnerabilities. Additionally, organizations should consider implementing alternative authentication methods that do not rely on continuous network connectivity for screen unlocking, such as local authentication caching or biometric authentication systems. The vulnerability demonstrates the importance of robust error handling in security-critical components and underscores the need for comprehensive testing of failure scenarios in authentication systems.