CVE-2016-3100 in KDE Frameworks
Summary
by MITRE
kinit in KDE Frameworks before 5.23.0 uses weak permissions (644) for /tmp/xauth-xxx-_y, which allows local users to obtain X11 cookies of other users and consequently capture keystrokes and possibly gain privileges by reading the file.
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Analysis
by VulDB Data Team • 10/09/2024
The vulnerability described in CVE-2016-3100 represents a critical privilege escalation and information disclosure issue within the KDE Frameworks kinit component. This flaw affects versions prior to 5.23.0 and stems from improper file permission handling during the creation of temporary X11 authentication files. The vulnerability specifically targets the /tmp/xauth-xxx-_y temporary file which is generated during X11 authentication processes, creating a persistent security risk for local users on affected systems.
The technical implementation of this vulnerability involves the kinit utility creating temporary files with overly permissive Unix file permissions of 644, which grants read access to all users on the system. This weak permission setting violates fundamental security principles of least privilege and proper file access control. The temporary file contains X11 authentication cookies that are essential for establishing graphical session connections, making these files highly valuable targets for malicious actors. The issue resides in the X11 authentication mechanism implementation where the system fails to properly secure temporary authentication artifacts, creating an attack surface that allows unauthorized access to graphical session contexts.
From an operational impact perspective, this vulnerability enables local users to perform unauthorized access to other users' X11 sessions through simple file reading operations. The consequences extend beyond mere information disclosure to potential privilege escalation opportunities, as X11 cookies can be used to intercept keystrokes, capture screen content, and manipulate graphical applications. Attackers can leverage this vulnerability to monitor user activities, steal session tokens, and potentially execute malicious actions within the context of other users' graphical sessions. The attack vector is particularly concerning because it requires minimal privileges and can be executed by any local user, making it a significant concern for multi-user systems and shared computing environments.
This vulnerability maps directly to CWE-732: Incorrect Permission Assignment for Critical Resource and CWE-276: Incorrect Permission Assignment, both of which address improper access control mechanisms. The issue also aligns with ATT&CK technique T1056.001: Input Injection - Man-in-the-Between, as it enables unauthorized interception of graphical session data. The security implications extend to privilege escalation scenarios where attackers can potentially leverage X11 session access to gain elevated privileges. The vulnerability demonstrates a failure in proper temporary file management and access control implementation, creating a persistent threat that remains active until the affected software is updated.
Mitigation strategies for this vulnerability require immediate software updates to KDE Frameworks version 5.23.0 or later, which properly implements secure temporary file creation with appropriate permissions. System administrators should also implement monitoring for unauthorized access attempts to temporary files in the /tmp directory and consider implementing additional security measures such as secure temporary file creation using proper umask settings or alternative authentication mechanisms. The fix addresses the root cause by ensuring that temporary X11 authentication files are created with restrictive permissions that prevent unauthorized access while maintaining proper functionality for legitimate users. Organizations should conduct thorough vulnerability assessments to identify systems running affected versions and implement comprehensive patch management processes to prevent exploitation of this and similar vulnerabilities in their environments.