CVE-2017-8288 in gnome-shell
Summary
by MITRE
gnome-shell 3.22 through 3.24.1 mishandles extensions that fail to reload, which can lead to leaving extensions enabled in the lock screen. With these extensions, a bystander could launch applications (but not interact with them), see information from the extensions (e.g., what applications you have opened or what music you were playing), or even execute arbitrary commands. It all depends on what extensions a user has enabled. The problem is caused by lack of exception handling in js/ui/extensionSystem.js.
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Analysis
by VulDB Data Team • 12/02/2022
The vulnerability identified as CVE-2017-8288 represents a critical security flaw in the GNOME Shell desktop environment affecting versions 3.22 through 3.24.1. This issue stems from inadequate exception handling within the JavaScript-based extension system, specifically in the js/ui/extensionSystem.js file. The flaw creates a persistent security risk where extensions that fail to reload properly remain enabled on the lock screen, exposing sensitive user information and system capabilities to unauthorized observers. The vulnerability operates at the intersection of desktop environment security and extension management, creating a scenario where malicious actors or curious bystanders can gain unauthorized access to information and potentially execute commands through compromised extensions.
The technical nature of this vulnerability falls under CWE-248, which addresses "Uncaught Exception" conditions in software systems. The flaw manifests when GNOME Shell fails to properly handle extension reload failures, allowing extensions to maintain their active state even when they should be disabled or terminated. This improper exception handling creates a persistent security boundary violation where the lock screen, which should provide isolation and protection, becomes a vector for information disclosure and potential command execution. The JavaScript-based nature of GNOME Shell extensions means that the vulnerability exists within the interpreted runtime environment, making it particularly challenging to detect and remediate through traditional binary patching methods.
The operational impact of CVE-2017-8288 extends beyond simple information disclosure to encompass potential privilege escalation and unauthorized application execution. When extensions remain active on the lock screen, they can expose detailed information about the user's running applications, media playback status, and other system activities. The severity of this exposure varies significantly based on the specific extensions enabled by the user, as different extensions may have varying levels of access to system resources and user data. This vulnerability directly maps to ATT&CK technique T1056.001, which covers "Input Injection: Keylogging", as extensions can potentially capture user input and system state information. The ability for bystanders to launch applications or execute commands through these persistent extensions creates a serious threat to user privacy and system integrity.
Mitigation strategies for CVE-2017-8288 require immediate system updates to GNOME Shell versions that address the exception handling flaw in extension management. Users should upgrade to GNOME Shell 3.24.2 or later, where proper exception handling has been implemented to prevent extensions from remaining active during reload failures. System administrators should conduct thorough audits of enabled extensions and disable any non-essential or untrusted extensions that could potentially exploit this vulnerability. The fix implemented in patched versions involves adding robust exception handling in the extension system to ensure that when extensions fail to reload, they are properly disabled rather than remaining active on the lock screen. Additionally, organizations should implement monitoring solutions to detect unusual extension behavior and establish policies for extension management that minimize the attack surface available through this vulnerability.