CVE-2005-2991 in ncompress
Summary
by MITRE
ncompress 4.2.4 and earlier allows local users to overwrite arbitrary files via a symlink attack on temporary files using (1) zdiff or (2) zcmp, a different vulnerability than CVE-2004-0970.
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Analysis
by VulDB Data Team • 07/11/2018
The vulnerability identified as CVE-2005-2991 affects the ncompress utility version 4.2.4 and earlier, presenting a significant security risk through improper handling of temporary files during execution of zdiff and zcmp commands. This flaw represents a symlink attack vulnerability that enables local users to manipulate the file system by creating symbolic links that point to sensitive target files, potentially leading to arbitrary file overwrites. The issue specifically manifests when these compression utilities create temporary files without adequate security checks, allowing malicious users to substitute their own files in place of the expected temporary files.
The technical implementation of this vulnerability stems from the insecure creation of temporary files within the compression utilities. When zdiff or zcmp execute, they generate temporary files in predictable locations without proper validation of file ownership or existence. This behavior creates a race condition window where an attacker can establish symbolic links with the same names as the expected temporary files, effectively redirecting the utility's write operations to arbitrary locations within the file system. The vulnerability operates under the broader category of insecure temporary file handling as classified by CWE-377, which specifically addresses the creation of temporary files with insecure permissions or predictable names.
From an operational standpoint, this vulnerability presents a serious risk to system integrity and data confidentiality. Local users who can execute the affected commands gain the ability to overwrite any file that the executing user has write permissions for, potentially compromising system security through privilege escalation or data manipulation attacks. The impact extends beyond simple file overwrites, as attackers could target critical system files, configuration data, or sensitive user information, leading to potential system compromise or data loss. The vulnerability's exploitation requires local access and the ability to create symbolic links, making it particularly concerning in multi-user environments where users may not have full system privileges.
The security implications of CVE-2005-2991 align with several ATT&CK techniques including privilege escalation through file system manipulation and defense evasion via exploitation of system utilities. This vulnerability demonstrates how seemingly benign system utilities can become attack vectors when proper security controls are not implemented. The flaw also relates to the broader category of command injection and file system attacks that attackers frequently target in enterprise environments. Organizations should consider this vulnerability as part of their comprehensive security posture assessment, particularly in environments where multiple users have access to system utilities that may be vulnerable to similar temporary file handling issues.
Mitigation strategies for this vulnerability primarily involve updating to ncompress versions 4.2.5 or later, which address the insecure temporary file creation behavior. System administrators should also implement proper file system permissions and access controls to limit the potential impact of such vulnerabilities. Additional protective measures include monitoring for unauthorized symbolic link creation in temporary directories and implementing discretionary access controls that prevent users from creating links in critical system areas. The vulnerability serves as a reminder of the importance of secure coding practices and proper input validation in system utilities, particularly those that handle file operations and temporary file creation. Organizations should conduct regular security assessments to identify and remediate similar vulnerabilities in their software ecosystems, as the principles underlying this flaw continue to be relevant in modern security contexts.