CVE-2004-0647 in Shorewall
Summary
by MITRE
shorewall 1.4.10c and earlier, and 2.0.x before 2.0.3a, allows local users to overwrite arbitrary files via a symlink attack on the chains-$$ temporary file.
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Analysis
by VulDB Data Team • 06/30/2021
The vulnerability identified as CVE-2004-0647 represents a critical file system security flaw affecting shorewall versions 1.4.10c and earlier, as well as 2.0.x versions before 2.0.3a. This issue stems from improper handling of temporary files during the execution of shorewall configuration processes, creating opportunities for local privilege escalation through symbolic link manipulation attacks. The vulnerability specifically targets the chains-$$ temporary file mechanism used by shorewall to manage firewall rule chains, where the temporary file creation process lacks proper security checks that would prevent malicious symlink exploitation.
The technical implementation of this vulnerability occurs when shorewall creates temporary files using predictable naming patterns combined with process identifiers, such as chains-$$ where $$ represents the process ID. Local attackers can exploit this predictability by creating symbolic links with the same names in the target directory before shorewall executes, causing the system to write sensitive data to locations controlled by the attacker rather than the intended temporary file location. This type of vulnerability falls under the category of time-of-check to time-of-use race conditions, which is classified as CWE-367, and represents a classic example of insecure temporary file handling that has been consistently documented in security literature as a common attack vector.
The operational impact of this vulnerability extends beyond simple file overwrites, as it enables attackers to potentially modify critical system files, inject malicious code into firewall configurations, or manipulate network security policies in ways that could compromise entire network infrastructures. Attackers exploiting this vulnerability can overwrite files with arbitrary content, potentially including system binaries, configuration files, or log data, leading to persistent access or complete system compromise. This vulnerability particularly affects systems where shorewall is used for network security policy management, making it a significant concern for enterprise environments that rely on proper firewall rule enforcement.
Mitigation strategies for CVE-2004-0647 should focus on both immediate patching and operational security improvements. The most effective immediate solution involves upgrading to shorewall versions 1.4.10d or 2.0.3a and later, which contain proper temporary file handling mechanisms that prevent symlink attacks. Additionally, system administrators should implement proper file system permissions and directory access controls to limit write access to shorewall temporary directories. The vulnerability demonstrates the importance of following secure coding practices such as those outlined in the OWASP Secure Coding Practices, particularly regarding temporary file creation and management. Organizations should also consider implementing monitoring solutions that can detect unauthorized file modifications in critical system directories, as this attack vector can be used to establish persistent backdoors or escalate privileges within the network security infrastructure. This vulnerability aligns with ATT&CK technique T1059.007 for privilege escalation and T1566 for social engineering, as it can be leveraged to gain unauthorized access to system resources through manipulation of legitimate system processes.