CVE-2014-7272 in Desktop Display Manager
Summary
by MITRE
Simple Desktop Display Manager (SDDM) before 0.10.0 allows local users to gain root privileges because code running as root performs write operations within a user home directory, and this user may have created links in advance (exploitation requires the user to win a race condition in the ~/.Xauthority chown case, but not other cases).
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Analysis
by VulDB Data Team • 02/17/2023
The vulnerability identified as CVE-2014-7272 affects Simple Desktop Display Manager (SDDM) versions prior to 0.10.0, presenting a significant privilege escalation risk within Linux desktop environments. This issue stems from improper handling of file permissions and ownership during the display manager's operation, specifically when managing the ~/.Xauthority file which serves as a critical authentication mechanism for X Window System sessions. The flaw allows local attackers to exploit a race condition that occurs when SDDM performs write operations in user home directories while running with root privileges, creating an avenue for unauthorized privilege elevation.
The technical implementation of this vulnerability involves a race condition scenario where SDDM executes code with elevated privileges while manipulating files within user home directories. When the display manager processes the ~/.Xauthority file, it performs chown operations that can be manipulated by malicious users who have pre-created symbolic links within their home directories. The attacker must successfully win the race condition specifically in the ~/.Xauthority chown case, though similar exploitation opportunities exist in other file operations within the user directory space. This race condition exploitation requires precise timing and control over the filesystem state, making it a sophisticated but achievable attack vector for determined adversaries.
The operational impact of this vulnerability extends beyond simple privilege escalation to potentially compromise entire desktop environments and underlying system security. When successfully exploited, local users can gain root access, enabling them to modify system files, install malicious software, access sensitive data, and establish persistent backdoors within the system. The vulnerability affects desktop environments that rely on SDDM as their display manager, particularly those running versions prior to 0.10.0, and represents a critical security gap that could be leveraged by attackers to establish footholds within target systems. The implications are particularly severe in multi-user environments where local access might be obtained through various attack vectors.
Mitigation strategies for CVE-2014-7272 primarily focus on upgrading to SDDM version 0.10.0 or later, which includes patches addressing the race condition and improper file handling issues. System administrators should also implement additional security measures such as restricting symbolic link creation in user home directories, monitoring for unusual file ownership changes, and ensuring proper file system permissions are maintained. The vulnerability aligns with CWE-367, which describes Time-of-Check to Time-of-Use (TOCTOU) race conditions, and can be mapped to ATT&CK techniques involving privilege escalation through local exploitation. Organizations should conduct comprehensive security assessments to identify systems running vulnerable SDDM versions and implement immediate patching procedures to eliminate this attack vector from their security posture.