CVE-2000-1136 in Elvis Tiny
Summary
by MITRE
elvis-tiny before 1.4-10 in Debian GNU/Linux, and possibly other Linux operating systems, allows local users to overwrite files of other users via a symlink attack.
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Analysis
by VulDB Data Team • 04/07/2019
The vulnerability described in CVE-2000-1136 represents a classic file system security flaw affecting the elvis-tiny text editor package in Debian GNU/Linux systems. This issue manifests as a privilege escalation vulnerability that enables local attackers to manipulate file permissions and potentially overwrite files owned by other users. The vulnerability specifically impacts versions of elvis-tiny prior to 1.4-10, making it a significant concern for systems running older package versions. The core problem stems from improper handling of temporary files during the editor's operation, creating opportunities for malicious users to exploit symbolic link attacks against the system.
The technical implementation of this vulnerability involves the manipulation of symbolic links within the file system to redirect file operations to unintended targets. When elvis-tiny processes files, it creates temporary files in predictable locations without proper security checks to verify the legitimacy of these temporary file paths. Attackers can exploit this behavior by creating symbolic links in the same directory where elvis-tiny would normally create temporary files, effectively causing the editor to write data to locations controlled by the attacker rather than the intended target. This type of vulnerability falls under the category of insecure temporary file handling, which is classified as CWE-377 and CWE-378 in the Common Weakness Enumeration catalog. The attack vector specifically aligns with the ATT&CK technique T1068, which describes the use of privilege escalation through exploitation of software vulnerabilities.
The operational impact of CVE-2000-1136 extends beyond simple file overwrites, potentially enabling more sophisticated attacks such as privilege escalation, data corruption, or even system compromise when combined with other vulnerabilities. Local users who can execute the elvis-tiny editor can leverage this flaw to gain unauthorized access to files owned by other users, potentially accessing sensitive information or modifying critical system files. The vulnerability is particularly concerning in multi-user environments where different users share the same system resources and file system permissions. Additionally, the widespread use of elvis-tiny across various Linux distributions makes this vulnerability potentially exploitable across a broad range of systems, especially those that have not been properly updated to patched versions.
Mitigation strategies for this vulnerability should focus on immediate patching of affected elvis-tiny packages to versions 1.4-10 or later, which contain proper security fixes for temporary file handling. System administrators should implement comprehensive vulnerability management processes to identify and remediate similar issues across all installed software packages. Additional protective measures include restricting user permissions to prevent unauthorized symbolic link creation in directories where critical applications operate, implementing proper file system permissions that limit write access to sensitive directories, and conducting regular security audits to identify potential symlink attack vectors. The vulnerability also underscores the importance of secure coding practices, particularly in the handling of temporary files and directory operations, as recommended by various security frameworks and standards including the OWASP Secure Coding Practices and NIST guidelines for secure software development. Organizations should also consider implementing monitoring solutions to detect suspicious file system activities that might indicate exploitation attempts of similar vulnerabilities.