CVE-2019-13228 in deepin-clone
Summary
by MITRE
deepin-clone before 1.1.3 uses a fixed path /tmp/repo.iso in the BootDoctor::fix() function to download an ISO file, 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. By winning a race condition to replace the /tmp/repo.iso symlink by an attacker controlled ISO file, further privilege escalation may be possible.
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Analysis
by VulDB Data Team • 10/17/2023
The vulnerability CVE-2019-13228 affects deepin-clone versions prior to 1.1.3 and represents a critical path traversal and symlink attack vector within the BootDoctor::fix() function. This flaw stems from the application's hardcoded use of the /tmp/repo.iso path for ISO file downloads, creating a predictable attack surface that malicious users can exploit through symbolic link manipulation. The issue manifests when the application follows symlinks in the specified temporary directory, allowing unprivileged users to craft malicious symlink structures that redirect file operations to arbitrary locations within the filesystem. The vulnerability operates under the principle of insecure temporary file handling as classified by CWE-377, where the use of predictable temporary file names creates opportunities for privilege escalation attacks.
The technical implementation of this vulnerability leverages a race condition scenario where an attacker can manipulate the symlink state of /tmp/repo.iso before the application attempts to write to it. This race condition occurs because the application does not validate the target of the symlink or implement proper atomic file operations when creating or replacing the temporary ISO file. The attacker's strategy involves creating a symlink pointing to a target location of their choice, then racing to replace the symlink with an attacker-controlled ISO file, effectively bypassing normal file system permissions and access controls. This approach aligns with ATT&CK technique T1068 which describes the exploitation of race conditions for privilege escalation, and T1548.001 which covers abuse of system permissions for privilege escalation.
The operational impact of this vulnerability extends beyond simple file manipulation as it creates a potential privilege escalation pathway within the system. While the content of the ISO file itself is not attacker-controlled, the ability to overwrite or create files in arbitrary locations allows attackers to potentially modify system-critical files, install malicious payloads, or corrupt system components. The vulnerability particularly affects systems where deepin-clone is installed with elevated privileges, as the application's operation may be performed with higher privileges than the attacking user. This scenario creates a significant security risk for desktop environments where users may have legitimate access to the clone utility but should not be able to modify system files outside their intended scope.
Mitigation strategies for this vulnerability require immediate patching of affected deepin-clone versions to 1.1.3 or later, which addresses the hardcoded path issue by implementing proper temporary file handling mechanisms. Organizations should also implement additional controls such as restricting write permissions to the /tmp directory, using more secure temporary file creation methods that avoid symlink traversal, and implementing proper input validation for all file operations. The fix should ensure atomic file creation operations that prevent race conditions, such as using file descriptor-based creation methods or implementing proper file locking mechanisms. Security monitoring should also be enhanced to detect suspicious symlink creation patterns in temporary directories, particularly around the /tmp/repo.iso path. System administrators should consider implementing the principle of least privilege for applications that perform system-level operations, ensuring that applications like deepin-clone do not operate with unnecessary elevated privileges when possible. This vulnerability demonstrates the importance of secure coding practices and proper temporary file management in preventing privilege escalation attacks through predictable path manipulation.