CVE-2016-1233 in fuse Package
Summary
by MITRE
An unspecified udev rule in the Debian fuse package in jessie before 2.9.3-15+deb8u2, in stretch before 2.9.5-1, and in sid before 2.9.5-1 sets world-writable permissions for the /dev/cuse character device, which allows local users to gain privileges via a character device in /dev, related to an ioctl.
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Analysis
by VulDB Data Team • 10/16/2024
The vulnerability described in CVE-2016-1233 represents a critical privilege escalation flaw within the Debian fuse package ecosystem, specifically affecting udev rule configurations that govern device file permissions. This issue stems from an improperly configured udev rule that inadvertently grants world-writable permissions to the /dev/cuse character device, creating a significant security weakness that can be exploited by local attackers to elevate their privileges. The vulnerability affects multiple Debian releases including jessie, stretch, and sid, with specific version thresholds indicating when the fix was implemented. The root cause lies in the improper handling of device permissions within the udev subsystem, which is responsible for managing device nodes in Linux systems.
The technical flaw manifests through the manipulation of udev rules that control how device files are created and managed within the /dev directory hierarchy. When the problematic udev rule executes, it creates the /dev/cuse device file with overly permissive permissions that allow any local user to write to this character device. This vulnerability specifically relates to the ioctl system call mechanism, which provides a way for user-space programs to communicate with device drivers. The combination of world-writable permissions and the ioctl interface creates a pathway for privilege escalation attacks, as malicious code can leverage these permissions to execute arbitrary operations with elevated privileges. This flaw falls under CWE-732, which describes improper permission assignment, and represents a classic example of insecure default permissions in device management.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass broader system compromise potential. Local users who can access the world-writable /dev/cuse device can exploit the ioctl interface to perform operations that would normally require root privileges, potentially allowing them to modify system files, install malicious software, or gain complete system control. The vulnerability is particularly dangerous because it requires no special privileges to exploit and can be triggered by any user account on the system. Attackers can leverage this weakness to establish persistent access, modify system configurations, or even create backdoor accounts. The attack surface is broad since the /dev/cuse device is typically accessible to all users and the ioctl interface provides multiple vectors for exploitation.
Mitigation strategies for CVE-2016-1233 focus on updating the affected Debian packages to versions that contain fixed udev rules with proper permission settings. System administrators should immediately apply the security patches available for jessie version 2.9.3-15+deb8u2, stretch version 2.9.5-1, and sid version 2.9.5-1, ensuring that the updated udev rules properly configure permissions for the /dev/cuse device. Additionally, security monitoring should include verification of device file permissions to detect any unauthorized changes to the /dev/cuse device or related character devices. Network administrators should also consider implementing runtime monitoring to detect suspicious ioctl operations on character devices, as outlined in the ATT&CK framework under privilege escalation techniques. The fix typically involves modifying the udev rule to set appropriate permissions using the MODE directive, ensuring that the device file is only accessible to the appropriate user groups rather than all users, thereby preventing unauthorized access and exploitation.