CVE-2019-13227 in deepin-clone
Summary
by MITRE
In GUI mode, deepin-clone before 1.1.3 creates a log file at the fixed path /tmp/.deepin-clone.log as root, and follows symlinks there. An unprivileged user can prepare a symlink attack there to create or overwrite files in arbitrary file system locations. The content is not attacker controlled.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 10/17/2023
The vulnerability identified as CVE-2019-13227 affects the deepin-clone utility in its graphical user interface mode, specifically targeting versions prior to 1.1.3. This issue represents a classic symlink race condition vulnerability that arises from improper handling of temporary file creation in a multi-user environment. The flaw manifests when the application operates in GUI mode and creates log files at a predictable fixed location within the system's temporary directory structure.
The technical implementation of this vulnerability stems from the application's design decision to place log files at /tmp/.deepin-clone.log with root privileges while simultaneously following symbolic links present in that location. This behavior creates a race condition window where an unprivileged user can manipulate the file system by creating a symbolic link that points to a target location of their choosing. The attack vector exploits the fundamental security principle that temporary files created with elevated privileges should not be susceptible to manipulation by unprivileged users through symbolic link attacks.
When an unprivileged user successfully executes this symlink attack, they can cause the deepin-clone utility to create or overwrite files in arbitrary locations within the file system. The vulnerability is categorized under CWE-376 as a "Poorly Specified Temporary File" and aligns with the broader category of insecure temporary file handling. The attack requires the malicious user to have write access to the /tmp directory and the ability to create symbolic links, which is typically available to all users on most Unix-like systems. The critical aspect of this vulnerability is that while the content written to the target location is not directly controlled by the attacker, the ability to place files at arbitrary locations with root privileges constitutes a significant escalation of privileges.
The operational impact of this vulnerability extends beyond simple file manipulation as it enables potential privilege escalation attacks that could allow an unprivileged user to modify system-critical files or inject malicious content into locations where root processes might later write. This weakness creates a persistent threat vector that could be exploited to compromise system integrity and potentially escalate privileges to root level access. The vulnerability is particularly concerning in multi-user environments where users may have legitimate reasons to access the system but should not be able to manipulate files owned by other users or the system itself. The attack can be executed without requiring any special privileges or knowledge of system internals, making it accessible to attackers with minimal technical expertise.
Mitigation strategies for this vulnerability involve implementing proper temporary file creation practices that avoid predictable paths and symbolic link following. The recommended approach includes using secure temporary file creation methods such as mkstemp() or similar functions that create files with proper permissions and avoid race conditions. System administrators should update to deepin-clone version 1.1.3 or later where the vulnerability has been patched. Additionally, implementing proper file system permissions and using tools like SELinux or AppArmor can provide additional layers of protection. The ATT&CK framework categorizes this as a privilege escalation technique under T1068, specifically related to "Local Port Knocking" and "Exploitation for Privilege Escalation" where attackers leverage insecure temporary file handling to gain elevated system privileges. Organizations should also conduct regular security audits to identify similar vulnerabilities in other applications and ensure that all temporary file operations follow secure coding practices that prevent symbolic link attacks.