CVE-2004-0851 in Net-Acct
Summary
by MITRE
The (1) write_list and (2) dump_curr_list functions in Net-Acct before 0.71 allows local users to overwrite arbitrary files via a symlink attack on temporary files.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 06/05/2019
The vulnerability identified as CVE-2004-0851 affects Net-Acct version 0.71 and earlier, presenting a significant security risk through improper handling of temporary files during list writing operations. This flaw exists in two distinct functions: write_list and dump_curr_list, which are critical components responsible for managing account information within the system. The vulnerability stems from the application's failure to properly validate file access permissions when creating temporary files, creating an exploitable race condition that can be leveraged by local attackers.
The technical implementation of this vulnerability involves a classic symlink attack pattern where malicious users can manipulate the temporary file creation process to redirect file operations to arbitrary locations on the filesystem. When the write_list and dump_curr_list functions execute, they create temporary files without proper security checks or atomic operations, allowing an attacker to establish symbolic links with the same names as the expected temporary files. This race condition occurs between the time when the application checks for file existence and when it actually writes to the file, providing a window for exploitation. The vulnerability is classified under CWE-367, which specifically addresses Time-of-Check to Time-of-Use (TOCTOU) flaws, where the state of a resource changes between validation and actual use.
The operational impact of this vulnerability is substantial as it allows local users to overwrite arbitrary files with potentially malicious content or gain unauthorized access to sensitive system resources. An attacker could leverage this weakness to modify critical system files, inject malicious code into the application, or escalate privileges within the system. The vulnerability particularly affects systems where Net-Acct is installed with elevated privileges, as successful exploitation could lead to complete system compromise. Additionally, this flaw aligns with ATT&CK technique T1059.001 for executing malicious code through command-line interfaces, and T1078 for gaining access to systems through legitimate credentials, as the attack requires only local access to the system.
Mitigation strategies for this vulnerability should include immediate patching of the Net-Acct application to version 0.71 or later, where the temporary file handling has been corrected. System administrators should implement proper file permission controls and ensure that temporary file creation uses atomic operations or secure temporary file creation functions that prevent symbolic link attacks. The implementation of proper input validation and file access controls within the application code is essential, including checking for the existence of temporary files before writing and using secure file creation methods that prevent race conditions. Organizations should also consider implementing monitoring solutions to detect suspicious file modification patterns and establish regular security audits to identify similar vulnerabilities in other applications. Network segmentation and privilege separation can further reduce the potential impact of successful exploitation, while regular security training for system administrators helps prevent the introduction of such vulnerabilities through poor coding practices.