CVE-1999-0803 in AIX eNetwork Firewall
Summary
by MITRE
The fwluser script in AIX eNetwork Firewall allows local users to write to arbitrary files via a symlink attack.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 06/05/2024
The fwluser script vulnerability in AIX eNetwork Firewall represents a critical path traversal flaw that enables local users to manipulate file system permissions and potentially escalate privileges. This vulnerability exists within the firewall management utilities of IBM AIX operating systems and specifically targets the fwluser script which is responsible for user account management within the network firewall environment. The issue stems from improper handling of symbolic links during file operations, creating a window of opportunity for malicious local users to redirect file write operations to unintended locations.
The technical implementation of this vulnerability involves the fwluser script failing to properly validate or sanitize file paths when processing symbolic links. When the script creates or modifies files, it does not adequately verify that the target file paths are legitimate and intended, allowing attackers to establish malicious symbolic links that redirect the script's file operations to sensitive system files or directories. This type of flaw falls under the CWE-367 category of Time-of-Check to Time-of-Use (TOCTOU) vulnerabilities, where the system checks file permissions at one point and then performs operations at a later point when the permissions may have changed.
The operational impact of this vulnerability extends beyond simple unauthorized file modification, as it can potentially enable privilege escalation attacks when combined with other system weaknesses. Local users who can execute the fwluser script can leverage this vulnerability to overwrite critical system files, modify user permissions, or inject malicious code into the firewall environment. The attack vector requires local system access but does not need network connectivity, making it particularly dangerous in environments where local privilege escalation is already possible. This vulnerability aligns with ATT&CK technique T1068 which covers local privilege escalation through system configuration weaknesses.
Mitigation strategies for this vulnerability should focus on immediate patching of the AIX eNetwork Firewall software, along with implementing proper file system permissions and monitoring for suspicious symbolic link creation patterns. System administrators should ensure that the fwluser script and related firewall utilities are properly secured through file permission controls and that symbolic link usage is restricted in sensitive system directories. Additionally, regular security audits should verify that no malicious symbolic links exist in firewall-related directories, and monitoring solutions should be configured to alert on unauthorized file system modifications that could indicate exploitation attempts. The vulnerability demonstrates the critical importance of proper input validation and file system access controls in security-sensitive applications, particularly those managing network infrastructure components where unauthorized access can compromise entire network security postures.