CVE-2003-0517 in mgetty
Summary
by MITRE
faxrunqd.in in mgetty 1.1.28 and earlier allows local users to overwrite files via a symlink attack on JOB files.
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Analysis
by VulDB Data Team • 06/14/2018
The vulnerability identified as CVE-2003-0517 affects the faxrunqd.in component within mgetty version 1.1.28 and earlier installations, representing a significant local privilege escalation risk through symbolic link manipulation. This flaw exists within the fax processing daemon that handles incoming and outgoing fax jobs, creating an insecure temporary file creation mechanism that can be exploited by local attackers to overwrite arbitrary files on the system. The vulnerability stems from improper handling of job files during fax processing operations, where the system creates temporary files without adequate security checks or atomic operations.
The technical implementation of this vulnerability involves a classic symlink attack pattern where an attacker creates symbolic links in strategic locations before the fax daemon processes fax jobs. When mgetty processes a fax job, it creates temporary files in predictable locations without validating the existence or ownership of these paths, allowing a malicious user to establish symbolic links that point to sensitive system files. This creates a race condition scenario where the attacker can control which file receives the data written by the fax daemon, effectively enabling arbitrary file overwrite operations. The vulnerability specifically targets the JOB file handling mechanism within the fax processing pipeline, where temporary files are created with predictable naming conventions and locations.
The operational impact of CVE-2003-0517 extends beyond simple file overwriting capabilities to potentially enable local privilege escalation and system compromise. An attacker exploiting this vulnerability can overwrite critical system files such as configuration files, binaries, or even system libraries, potentially leading to unauthorized privilege elevation or complete system takeover. The vulnerability affects systems where mgetty is installed and running with sufficient privileges to process fax jobs, typically including systems with fax servers or multi-user environments where fax functionality is enabled. This flaw is particularly dangerous in enterprise environments where fax services might be running with elevated privileges or where multiple users have access to the system.
Mitigation strategies for this vulnerability require immediate patching of mgetty installations to versions that address the insecure file handling behavior. System administrators should ensure that all instances of mgetty are updated to versions that implement proper atomic file creation mechanisms and validate file paths before processing. Additional protective measures include restricting file permissions on fax-related directories, implementing proper file ownership controls, and monitoring for suspicious symbolic link creation patterns in fax processing directories. The vulnerability aligns with CWE-377: Insecure Temporary File and CWE-378: Creation of Temporary File With Insecure Permissions, both of which are categorized under the broader category of insecure file handling practices. From an attacker perspective, this vulnerability maps to ATT&CK technique T1059.007 for privilege escalation and T1078 for legitimate credentials use, as it allows attackers to manipulate system files through legitimate fax processing operations. Organizations should implement comprehensive monitoring for unauthorized symbolic link creation in fax-related directories and establish proper access controls to prevent local users from creating malicious symlinks in system directories.