CVE-2018-19637 in Supportutils
Summary
by MITRE
Supportutils, before version 3.1-5.7.1, wrote data to static file /tmp/supp_log, allowing local attackers to overwrite files on systems without symlink protection
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Analysis
by VulDB Data Team • 07/26/2023
The vulnerability identified as CVE-2018-19637 affects the supportutils package, a utility commonly used for collecting system information and logs for technical support purposes. This flaw exists in versions prior to 3.1-5.7.1 and represents a significant security weakness that can be exploited by local attackers to manipulate system files. The issue stems from the package's improper handling of temporary file creation, specifically the use of a static file path that lacks adequate security controls. The affected file path /tmp/supp_log demonstrates poor security design practices where the utility creates a fixed temporary file without proper validation or protection mechanisms. This vulnerability directly relates to CWE-377, which addresses insecure temporary file creation, and CWE-378, which covers the creation of temporary files with insecure permissions. The flaw allows attackers to potentially overwrite arbitrary files on the system, making it particularly dangerous in environments where local privilege escalation or file manipulation could lead to broader system compromise.
The technical implementation of this vulnerability occurs when supportutils executes and attempts to write log data to the predetermined /tmp/supp_log location. Since this file path is static and predictable, an attacker can exploit the system's lack of symlink protection to create a symbolic link that points to a sensitive system file. When the supportutils process runs and attempts to write data to what it believes is the temporary log file, it actually overwrites the target file that the symbolic link points to. This type of attack falls under the ATT&CK technique T1059.001 for command and script injection, as well as T1070.004 for file deletion or modification. The vulnerability is particularly concerning because it requires no special privileges beyond local access, making it accessible to any user who can execute the supportutils utility. The attack vector is straightforward yet effective, leveraging the predictable nature of static file paths and the absence of proper file access controls.
The operational impact of CVE-2018-19637 extends beyond simple file overwriting, as it can potentially enable more sophisticated attacks depending on the target files. If an attacker successfully overwrites critical system files such as configuration files, binary executables, or log files, they could disrupt system operations, escalate privileges, or maintain persistent access. The vulnerability is especially dangerous in multi-user environments where different users may have varying levels of access to the supportutils utility. The lack of symlink protection in the temporary file creation process means that even users with minimal privileges could potentially exploit this weakness. Organizations running affected versions of supportutils should consider the broader implications of this vulnerability, as it could be used as a stepping stone for more advanced attacks. The vulnerability also highlights the importance of proper file handling practices and the need for robust temporary file management in security-critical applications.
Mitigation strategies for CVE-2018-19637 should focus on immediate remediation through version updates to supportutils 3.1-5.7.1 or later, which contain the necessary patches to address the temporary file handling issue. System administrators should also implement additional protective measures such as ensuring proper symlink protection mechanisms are in place, using more secure temporary file creation methods that generate unique file names, and implementing proper file permissions for temporary directories. The use of secure temporary file creation functions that are resistant to race conditions should be enforced in all applications that handle temporary file operations. Organizations should conduct vulnerability assessments to identify any systems running affected versions of supportutils and ensure that all instances are updated promptly. Additionally, monitoring for unauthorized file modifications in temporary directories can help detect potential exploitation attempts. The implementation of proper input validation and file access controls should be part of broader security hardening efforts, particularly in environments where local access is possible. Regular security audits of system utilities and applications should include checks for similar temporary file handling vulnerabilities that could be exploited in similar manners.