CVE-2004-2097 in Linux
Summary
by MITRE
Multiple scripts on SuSE Linux 9.0 allow local users to overwrite arbitrary files via a symlink attack on (1) /tmp/fvwm-bug created by fvwm-bug, (2) /tmp/wmmenu created by wm-oldmenu2new, (3) /tmp/rates created by x11perfcomp, (4) /tmp/xf86debug.1.log created by xf86debug, (5) /tmp/.winpopup-new created by winpopup-send.sh, or (6) /tmp/initrd created by lvmcreate_initrd.
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Analysis
by VulDB Data Team • 06/25/2018
This vulnerability represents a classic symlink attack scenario affecting multiple system scripts on SuSE Linux 9.0 installations. The flaw stems from insecure temporary file creation practices where scripts fail to properly validate or create temporary files with unique names, instead relying on predictable paths that can be exploited by local users. The vulnerability is categorized under CWE-377 as insecure temporary file creation and aligns with ATT&CK technique T1059.007 for script-based execution. Multiple scripts across different subsystems exhibit this weakness, creating a broad attack surface that could be leveraged by malicious local users to overwrite arbitrary files with potentially elevated privileges.
The technical implementation of this vulnerability occurs when scripts create temporary files in the /tmp directory without proper security measures such as using unique filenames or setting appropriate file permissions. The affected scripts include fvwm-bug which creates /tmp/fvwm-bug, wm-oldmenu2new generating /tmp/wmmenu, x11perfcomp producing /tmp/rates, xf86debug creating /tmp/xf86debug.1.log, winpopup-send.sh forming /tmp/.winpopup-new, and lvmcreate_initrd producing /tmp/initrd. Each of these temporary files is created with predictable names that can be preempted by attackers using symbolic links. This creates a race condition scenario where an attacker can establish a symlink before the vulnerable script creates its temporary file, causing the script to write data to the attacker-controlled location instead of the intended temporary file.
The operational impact of this vulnerability is significant as it allows local users to potentially overwrite critical system files or configuration data with malicious content. Attackers could exploit this to escalate privileges, corrupt system integrity, or establish persistent access mechanisms. The vulnerability affects multiple subsystems including window management, performance testing, debugging utilities, and system initialization processes. This widespread exposure across different script categories indicates a systemic security issue in how temporary files are handled within the SuSE Linux 9.0 distribution. The attack vector requires local system access but can result in substantial damage to system confidentiality, integrity, and availability. The vulnerability is particularly concerning because it affects core system utilities and could be exploited during normal system operation when these scripts are executed.
Mitigation strategies should focus on implementing secure temporary file creation practices that prevent symlink attacks. The primary solution involves modifying vulnerable scripts to use secure temporary file creation functions that ensure unique filenames and proper file permissions. This includes using functions like mkstemp or creating temporary files with random names in directories with appropriate permissions. System administrators should also implement proper file permission controls and consider using the secure_tmpfs mount option for /tmp directories. Additionally, the vulnerability highlights the importance of following secure coding practices and conducting regular security audits of system scripts. The fix should be applied at the source level by ensuring that temporary files are created atomically and that the scripts validate the ownership and permissions of temporary file locations before writing to them. Organizations should also implement monitoring for suspicious file creation patterns and consider implementing mandatory access controls to limit the potential impact of such vulnerabilities. This vulnerability serves as a reminder of the critical importance of secure temporary file handling in Unix-like systems and the need for comprehensive security testing of system utilities.