CVE-2011-4617 in Virtualenv
Summary
by MITRE
virtualenv.py in virtualenv before 1.5 allows local users to overwrite arbitrary files via a symlink attack on a certain file in /tmp/.
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Analysis
by VulDB Data Team • 11/28/2021
The vulnerability identified as CVE-2011-4617 resides within the virtualenv Python packaging tool, specifically in the virtualenv.py script version 1.4 and earlier. This flaw represents a classic symlink attack vulnerability that exploits insecure temporary file handling mechanisms. The vulnerability occurs when virtualenv creates temporary files in the /tmp/ directory without proper validation of symbolic link targets, creating a race condition scenario where an attacker can manipulate the file system to redirect file operations to arbitrary locations.
The technical implementation of this vulnerability stems from the improper handling of temporary files during the virtualenv creation process. When the tool executes, it generates temporary files in the /tmp/ directory to store intermediate data and configuration information. The flaw manifests because virtualenv does not verify whether these temporary file paths are legitimate or if they have been replaced with symbolic links by an attacker. This insecure practice allows malicious users to place symbolic links in the /tmp/ directory that point to sensitive system files, enabling them to overwrite critical files with arbitrary content during the virtualenv execution process.
The operational impact of this vulnerability extends beyond simple file overwrites and represents a significant privilege escalation risk. Local users who can execute virtualenv commands can leverage this weakness to modify system files, potentially compromising the integrity of the entire system. The attack vector specifically targets the /tmp/ directory which is typically world-writable and accessible to all users, making this vulnerability particularly dangerous in multi-user environments. Attackers can exploit this to replace configuration files, binaries, or other critical system resources with malicious versions, potentially leading to persistent backdoors or complete system compromise.
This vulnerability maps directly to CWE-377: Insecure Temporary File and CWE-378: Creation of Temporary File With Insecure Permissions, both of which are categorized under weak temporary file handling practices. From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1059.001 for executing commands and T1548.001 for privilege escalation through the manipulation of system files. The vulnerability also relates to T1078.004 for legitimate credentials and T1566.001 for social engineering through file system manipulation. The exploitability of this vulnerability is enhanced by the fact that virtualenv is commonly used in development environments and automated deployment systems, making it a prime target for attackers seeking to establish persistent access or escalate privileges within compromised systems.
The recommended mitigation strategy involves upgrading to virtualenv version 1.5 or later, where the developers implemented proper symlink validation and temporary file handling mechanisms. System administrators should also consider implementing additional security controls such as restricting write access to the /tmp/ directory for non-privileged users, using more secure temporary file creation methods that check for symbolic links, and implementing proper file system permissions. Organizations should conduct regular security audits to identify and remediate similar vulnerabilities in other tools and applications that may exhibit similar insecure temporary file handling behaviors. Additionally, implementing process monitoring and file integrity checking mechanisms can help detect unauthorized modifications to critical system files that might result from exploitation of this vulnerability.