CVE-2007-6209 in zsh
Summary
by MITRE
Util/difflog.pl in zsh 4.3.4 allows local users to overwrite arbitrary files via a symlink attack on temporary files.
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Analysis
by VulDB Data Team • 07/29/2021
The vulnerability identified as CVE-2007-6209 affects the zsh shell version 4.3.4 and specifically targets the util/difflog.pl utility. This represents a classic symlink attack scenario where local users can exploit improper handling of temporary files during the execution of the difflog.pl script. The flaw stems from the utility's failure to properly validate or secure temporary file creation processes, creating opportunities for malicious actors to manipulate the file system through symbolic link manipulation.
The technical implementation of this vulnerability resides in the improper use of temporary file mechanisms within the difflog.pl script. When the script executes, it creates temporary files without adequate security measures to prevent symlink attacks. An attacker can place a malicious symbolic link in the directory where the script expects to create temporary files, causing the script to write data to locations other than its intended target. This type of vulnerability falls under CWE-377 which specifically addresses insecure temporary file handling practices and represents a significant weakness in the principle of least privilege.
The operational impact of this vulnerability extends beyond simple file overwrites, as it allows attackers to potentially modify critical system files or configuration data that the zsh utility might be processing. Since zsh is a widely used shell implementation, particularly in unix-like operating systems, exploitation of this vulnerability could enable attackers to gain unauthorized access to system resources or manipulate shell behavior in ways that could compromise system integrity. The attack vector requires local access but does not need elevated privileges, making it particularly concerning for environments where multiple users share system resources.
Mitigation strategies for this vulnerability involve immediate patching of affected zsh installations to versions that properly address the symlink attack surface in temporary file creation. System administrators should also implement proper file system permissions and ensure that temporary directories are properly secured with appropriate access controls. The remediation approach should align with the principle of least privilege as outlined in the MITRE ATT&CK framework, particularly focusing on privilege escalation and defense evasion techniques. Additionally, regular security audits should verify that temporary file handling mechanisms in all shell utilities follow secure coding practices to prevent similar vulnerabilities from being introduced in future releases. Organizations should also consider implementing file system monitoring to detect suspicious symlink creation patterns that could indicate attempts to exploit this class of vulnerability.