CVE-2002-1119 in Python
Summary
by MITRE
os._execvpe from os.py in Python 2.2.1 and earlier creates temporary files with predictable names, which could allow local users to execute arbitrary code via a symlink attack.
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Analysis
by VulDB Data Team • 07/19/2019
The vulnerability identified as CVE-2002-1119 represents a critical security flaw in Python's os module affecting versions 2.2.1 and earlier. This issue stems from the implementation of the os._execvpe function which is responsible for executing programs with environment variables. The vulnerability specifically manifests in how the function handles temporary file creation during program execution, creating a predictable naming pattern that adversaries can exploit through symlink attacks.
The technical flaw occurs within the os._execvpe implementation where temporary files are created with predictable names such as /tmp/... This predictability allows local attackers to create symbolic links with the same names before the vulnerable function creates its temporary files. When the function executes and attempts to write to these predictable paths, the symbolic links redirect the writes to attacker-controlled locations, potentially enabling privilege escalation or arbitrary code execution. The vulnerability is classified under CWE-353 as "Missing Security Check for Unpredictable Input" and relates to CWE-354 as "Improper Check for Unpredictable Input" within the broader context of security weaknesses in software implementations.
The operational impact of this vulnerability is significant for systems running affected Python versions, particularly in multi-user environments where local attackers may have limited access but can leverage this flaw to gain elevated privileges. Attackers can exploit this by creating symbolic links in the temporary directory with predictable names, then triggering the vulnerable os._execvpe function through various means such as invoking shell commands or executing Python scripts that utilize this function internally. The attack vector is particularly dangerous because it requires minimal privileges to execute and can potentially lead to complete system compromise depending on the context in which the vulnerable function is called.
Mitigation strategies for CVE-2002-1119 focus primarily on upgrading to Python versions 2.2.2 and later where the vulnerability has been addressed through improved temporary file handling mechanisms. Organizations should also implement proper file system permissions and access controls to limit the ability of local users to create symbolic links in critical directories. The ATT&CK framework categorizes this vulnerability under T1068 as "Exploitation for Privilege Escalation" and T1548.001 as "Abuse of Cloud Compute Infrastructure" when considering the broader attack surface. System administrators should also monitor for suspicious symbolic link creation patterns and implement security measures such as SELinux or AppArmor policies to restrict temporary file operations. Additionally, the vulnerability highlights the importance of following secure coding practices including proper randomization of temporary file names and implementing atomic file creation operations to prevent race conditions that attackers can exploit through symlink attacks.