CVE-2015-1331 in lxc
Summary
by MITRE
lxclock.c in LXC 1.1.2 and earlier allows local users to create arbitrary files via a symlink attack on /run/lock/lxc/*.
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Analysis
by VulDB Data Team • 06/09/2022
The vulnerability identified as CVE-2015-1331 affects the Linux Containers project version 1.1.2 and earlier, specifically within the lxclock.c component. This flaw represents a classic symlink attack scenario that enables local attackers to manipulate file creation operations in a manner that can compromise system integrity and potentially escalate privileges. The issue arises from inadequate validation of symbolic link references during the locking mechanism implementation, creating an opportunity for malicious users to exploit the system's file handling processes.
The technical implementation of this vulnerability stems from the improper handling of file paths in the LXC container management system. When lxclock.c attempts to create lock files in the /run/lock/lxc/ directory structure, it does not sufficiently verify whether the target path represents a legitimate file or has been replaced with a symbolic link by an attacker. This weakness allows adversaries to pre-create symbolic links in the target directory, causing the legitimate locking mechanism to write data to arbitrary locations on the filesystem. The flaw operates under CWE-367 which specifically addresses Time-of-Check to Time-of-Use vulnerabilities, where the system's state changes between the validation phase and the actual operation execution.
From an operational perspective, this vulnerability presents significant risks to containerized environments as it allows local users to potentially overwrite critical system files or create malicious files with elevated privileges. Attackers could exploit this weakness to establish persistence mechanisms, modify container configuration files, or even inject malicious code into the container management system. The impact extends beyond simple file creation as it can potentially enable privilege escalation scenarios where local users gain elevated system privileges through manipulation of the locking mechanism. This vulnerability directly relates to ATT&CK technique T1059 which involves executing malicious code through legitimate system processes, and T1068 which covers privilege escalation through local exploits.
The mitigation strategies for CVE-2015-1331 primarily involve upgrading to LXC versions 1.1.3 and later where the vulnerability has been addressed through proper path validation and symlink checking mechanisms. System administrators should also implement additional security controls such as restrictive file permissions on the /run/lock/lxc/ directory structure and monitoring for unauthorized symbolic link creation. The fix typically involves ensuring that all file operations check for and resolve symbolic links before performing any file creation or modification operations, thereby preventing the TOCTOU race condition that enables this attack. Organizations should also consider implementing automated patch management processes to ensure timely deployment of security updates across containerized environments and maintain comprehensive monitoring of system integrity to detect potential exploitation attempts.