CVE-2018-14424 in GDM
Summary
by MITRE
The daemon in GDM through 3.29.1 does not properly unexport display objects from its D-Bus interface when they are destroyed, which allows a local attacker to trigger a use-after-free via a specially crafted sequence of D-Bus method calls, resulting in a denial of service or potential code execution.
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Analysis
by VulDB Data Team • 05/02/2023
The vulnerability identified as CVE-2018-14424 affects the GNOME Display Manager daemon version 3.29.1 and earlier, presenting a critical security flaw in the D-Bus interface implementation. This issue stems from improper handling of display object lifecycle management within the GDM daemon process, creating a persistent security weakness that can be exploited by local attackers to execute arbitrary code or cause system denial of service.
The technical root cause of this vulnerability lies in the daemon's failure to properly unexport display objects from the D-Bus interface when these objects are destroyed or removed from memory. This mismanagement creates a use-after-free condition where malicious D-Bus method calls can target already freed memory locations, leading to unpredictable behavior. The flaw operates through a carefully crafted sequence of D-Bus interactions that exploit the timing gap between object destruction and D-Bus interface cleanup, allowing attackers to manipulate memory contents and potentially execute malicious code.
From an operational perspective, this vulnerability presents significant risk to systems running affected versions of GDM, as local attackers with minimal privileges can leverage this flaw to escalate their privileges or cause system instability. The potential for code execution makes this particularly dangerous in environments where GDM is used as a primary display manager, as attackers could gain unauthorized access to user sessions or system resources. The denial of service aspect further compounds the risk by potentially rendering the display manager unusable and disrupting user authentication processes.
The vulnerability aligns with CWE-416, which addresses use-after-free conditions in software implementations, and demonstrates how improper resource management can create persistent security flaws. This weakness can be mapped to ATT&CK technique T1068, which covers local privilege escalation through the exploitation of software vulnerabilities, and T1489, covering denial of service attacks through system resource manipulation. The attack surface is particularly concerning as it requires only local access and can be executed without elevated privileges, making it an attractive target for attackers seeking to compromise system integrity.
Mitigation strategies should prioritize immediate patching of affected GDM versions to 3.29.2 or later, which contain the necessary fixes for proper D-Bus object cleanup. System administrators should also implement monitoring for unusual D-Bus activity patterns and consider restricting local user access to D-Bus interfaces where possible. Additional defensive measures include regular security audits of D-Bus interface implementations and ensuring proper memory management practices are followed during object lifecycle transitions. Organizations should also consider implementing least privilege principles for GDM daemon processes and monitoring for potential exploitation attempts through automated security tools.