CVE-2004-0422 in Flim
Summary
by MITRE
flim before 1.14.3 creates temporary files insecurely, which allows local users to overwrite arbitrary files of the Emacs user via a symlink attack.
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Analysis
by VulDB Data Team • 09/05/2019
The vulnerability identified as CVE-2004-0422 affects the flim package version 1.14.2 and earlier, which is a mail client component for the Emacs text editor. This issue represents a classic insecure temporary file creation flaw that enables local privilege escalation through symlink attacks. The vulnerability stems from the flim package's failure to properly handle temporary file creation mechanisms during file operations, creating opportunities for malicious users to manipulate the system's file access patterns.
The technical flaw manifests when flim creates temporary files without implementing proper security measures to prevent symbolic link attacks. Specifically, the package uses predictable temporary file names and does not verify the existence of these files before creating them, allowing attackers to establish symbolic links in the temporary file path. This insecure practice violates fundamental security principles for temporary file handling and creates a race condition where an attacker can substitute a legitimate temporary file with a malicious symlink pointing to a target file they wish to overwrite. The vulnerability is classified under CWE-377 as insecure temporary file creation and falls under the broader category of CWE-378 which addresses insecure temporary file creation with predictable names.
When exploited, this vulnerability allows local users to overwrite arbitrary files owned by the Emacs user, potentially leading to privilege escalation or system compromise. The attack vector requires the attacker to have local access to the system and the ability to create symbolic links in the temporary file directory. The operational impact extends beyond simple file overwriting, as it could enable attackers to modify critical system files, configuration data, or even executable programs that are processed by Emacs or related applications. This type of vulnerability is particularly dangerous in multi-user environments where different users might be running Emacs processes with elevated privileges or access to sensitive data.
The attack scenario typically involves an attacker creating a symbolic link in the temporary file path that points to a target file they wish to modify, then triggering the flim package to create a temporary file at that location. Once the temporary file creation occurs, the symlink is resolved, and the attacker's target file gets overwritten with the contents of the malicious data. This vulnerability aligns with ATT&CK technique T1059.006 for execution through scripts and T1548.001 for privilege escalation through legitimate credentials. Mitigation strategies include upgrading to flim version 1.14.3 or later, implementing proper temporary file handling with unique naming schemes, using secure file creation functions that check for existing files, and restricting write permissions on temporary directories. System administrators should also consider implementing monitoring for suspicious file access patterns and ensuring that all software components are regularly updated to address known vulnerabilities. The vulnerability demonstrates the importance of following secure coding practices for temporary file management and highlights the risks associated with legacy software components that may not implement modern security controls.