CVE-2008-4966 in linux-patch-openswan
Summary
by MITRE
linux-patch-openswan 2.4.12 allows local users to overwrite arbitrary files via a symlink attack on (a) /tmp/snap##### and (b) /tmp/nightly##### temporary files, related to the (1) maysnap and (2) maytest scripts.
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Analysis
by VulDB Data Team • 10/13/2018
The vulnerability described in CVE-2008-4966 represents a critical local privilege escalation issue affecting the linux-patch-openswan 2.4.12 implementation. This flaw stems from insecure temporary file creation practices within the maysnap and maytest scripts that are part of the openswan package used for IPsec configuration and management. The vulnerability specifically targets the creation of temporary files in the /tmp directory using predictable naming patterns such as snap##### and nightly#####, where the # characters represent numeric placeholders. Attackers can exploit this weakness by creating symbolic links with these predictable names before the vulnerable scripts execute, thereby enabling them to overwrite arbitrary files on the system with arbitrary content.
The technical exploitation of this vulnerability leverages the fundamental principle of time-of-check to time-of-use (TOCTOU) race conditions commonly classified under CWE-367. When the maysnap and maytest scripts create temporary files in the /tmp directory without proper atomic operations or secure file creation mechanisms, they become susceptible to symlink attacks. The scripts execute with elevated privileges, typically running as root or with administrative permissions, making the potential impact of arbitrary file overwrites particularly severe. An attacker who successfully places a symbolic link in the /tmp directory before the script execution can cause the script to write data to the target file specified by the symlink, potentially overwriting critical system files, configuration files, or even executable binaries that could be leveraged for privilege escalation.
The operational impact of this vulnerability extends beyond simple file overwrites and represents a significant threat to system integrity and availability. Attackers can leverage this weakness to modify system configuration files, inject malicious code into executable components, or manipulate critical log files to obscure their activities. The vulnerability affects systems running the affected version of openswan, which was commonly used for securing network communications through IPsec implementations. This weakness particularly impacts enterprise environments where IPsec is deployed for site-to-site or remote access VPN connections, as the compromised systems could potentially be used to establish persistent access or disrupt network security policies. The vulnerability's exploitation requires local access to the system, making it particularly dangerous in multi-user environments where attackers might gain initial access through other means and then leverage this weakness for privilege escalation.
Mitigation strategies for CVE-2008-4966 should focus on immediate patching of the affected openswan package to version 2.4.13 or later, which includes proper temporary file creation mechanisms that prevent symlink attacks. System administrators should implement the principle of least privilege by ensuring that the maysnap and maytest scripts run with minimal necessary privileges and avoid executing with root privileges when possible. The implementation of secure temporary file creation practices, such as using mkstemp() or similar atomic file creation functions, can prevent the race condition that enables this attack. Additionally, monitoring for suspicious symbolic link creation patterns in the /tmp directory and implementing file integrity monitoring solutions can help detect exploitation attempts. Organizations should also consider implementing the ATT&CK technique T1059.007 for command and script injection to detect and prevent malicious script execution, while also applying the principle of defense in depth by restricting write permissions to the /tmp directory for non-root users. The vulnerability highlights the importance of secure coding practices and proper file handling mechanisms in system administration tools, as outlined in the Common Weakness Enumeration standards for secure temporary file creation and race condition prevention.