CVE-2005-4536 in libmail-audit-perl
Summary
by MITRE
Mail::Audit module in libmail-audit-perl 2.1-5, when logging is enabled without a default log file specified, uses predictable log filenames, which allows local users to overwrite arbitrary files via a symlink attack on the [PID]-audit.log temporary file.
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Analysis
by VulDB Data Team • 07/27/2019
The vulnerability described in CVE-2005-4536 resides within the Mail::Audit Perl module version 2.1-5, specifically within its logging mechanism when the module operates without a predefined log file destination. This flaw manifests when the module's logging functionality is enabled but no explicit log file path is configured by the system administrator or application developer. The module automatically generates temporary log filenames using a predictable naming convention that incorporates the process identifier or PID of the running instance. This predictable pattern creates a significant security risk because it allows local attackers to manipulate the logging process through symbolic link attacks against the generated temporary files.
The technical implementation of this vulnerability stems from the module's failure to properly validate or sanitize the temporary file creation process. When logging is enabled without specifying a default log file, the Mail::Audit module creates a temporary file named using the pattern [PID]-audit.log where PID represents the process identifier. This predictable naming scheme enables attackers to establish symbolic links with the same names in the directory where the module creates its temporary files. When the module attempts to write to what it believes is a legitimate log file, it actually writes to the target of the attacker-controlled symbolic link, potentially allowing arbitrary file overwrite operations.
The operational impact of this vulnerability extends beyond simple file overwrites, as it provides attackers with a mechanism to manipulate system files and potentially escalate privileges. Attackers can exploit this weakness to overwrite critical system files, configuration files, or even files owned by other users or system processes. The vulnerability is particularly concerning because it requires minimal privileges to exploit, as it only necessitates local access to the system where the vulnerable module is installed. The attack vector is straightforward: an attacker creates a symbolic link with the predictable filename pattern before the module runs, then triggers the logging functionality to cause the module to write to the attacker-controlled target file.
This vulnerability aligns with several established security frameworks including CWE-310, which covers cryptographic weakness, and CWE-312, which addresses cleartext storage of sensitive information, though the primary classification relates to improper file handling and predictable temporary file names. From an ATT&CK perspective, this vulnerability maps to T1059.007 for the execution of code through the Mail::Audit module and T1499.004 for the potential for data destruction through file overwrites. The exploitability of this issue demonstrates poor input validation and inadequate temporary file handling practices that violate fundamental security principles of least privilege and secure coding practices. Organizations using libmail-audit-perl versions prior to the patched release should immediately implement mitigations including proper log file configuration, restricting write access to directories where temporary files might be created, and ensuring that symbolic link attacks are properly prevented through system hardening measures.
The remediation approach for this vulnerability involves multiple layers of defense including immediate patching of the vulnerable module, configuration changes to ensure explicit log file paths are specified, and implementation of proper temporary file handling mechanisms. System administrators should configure the Mail::Audit module to use explicit log file paths rather than relying on default temporary file creation. Additionally, the operating system should be configured to prevent symbolic link attacks by ensuring that temporary directories are properly secured with appropriate permissions and that the module does not run with elevated privileges when creating temporary files. This vulnerability serves as a critical reminder of the importance of secure temporary file handling in software development and the necessity of implementing proper input validation and file access controls to prevent predictable file manipulation attacks.