CVE-2014-3986 in Lynis
Summary
by MITRE
include/tests_webservers in Lynis before 1.5.5 allows local users to overwrite arbitrary files via a symlink attack on a /tmp/lynis.*.unsorted file with an easily determined name.
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Analysis
by VulDB Data Team • 03/22/2022
The vulnerability identified as CVE-2014-3986 resides within the Lynis security auditing tool, specifically in the handling of temporary files during web server testing procedures. This flaw affects versions prior to 1.5.5 and represents a classic symlink attack scenario that enables local privilege escalation through file overwrite operations. The vulnerability manifests when the tool creates temporary files in the /tmp directory with predictable naming conventions, making them susceptible to manipulation by malicious local users who can establish symbolic links to target sensitive system files.
The technical implementation of this vulnerability stems from inadequate temporary file handling practices within the include/tests_webservers component of Lynis. When the tool executes web server tests, it generates temporary files with names following the pattern /tmp/lynis.*.unsorted where the asterisk represents easily guessable identifiers. Local attackers can exploit this predictability by creating symbolic links with the same names in the /tmp directory before the legitimate file creation occurs. This race condition allows attackers to redirect file operations to arbitrary locations, potentially overwriting critical system files or configuration data with malicious content.
The operational impact of CVE-2014-3986 extends beyond simple file overwrites, as it can enable privilege escalation attacks when the Lynis tool is executed with elevated privileges. Since the tool typically requires root access to perform comprehensive security audits, local users who can manipulate temporary files gain the ability to modify system-critical resources. This vulnerability aligns with CWE-367, which addresses Time-of-Check to Time-of-Use (TOCTOU) race conditions, and represents a common attack pattern documented in the MITRE ATT&CK framework under privilege escalation techniques. The attack vector specifically maps to T1068, which describes local privilege escalation through exploitation of software vulnerabilities.
Mitigation strategies for this vulnerability require immediate patching to Lynis version 1.5.5 or later, where the developers implemented proper temporary file handling mechanisms. Organizations should ensure that all instances of Lynis across their infrastructure are updated to prevent exploitation. Additional defensive measures include implementing proper file permissions for the /tmp directory, using secure temporary file creation methods with unique identifiers, and monitoring for suspicious symbolic link creation activities. System administrators should also consider implementing file integrity monitoring solutions to detect unauthorized modifications to critical system files that may result from successful exploitation of this vulnerability. The fix addresses the root cause by employing atomic file creation techniques that prevent the race condition, thereby eliminating the window of opportunity for symlink-based attacks.