CVE-2019-13404 in Python
Summary
by MITRE
** DISPUTED ** The MSI installer for Python through 2.7.16 on Windows defaults to the C:\Python27 directory, which makes it easier for local users to deploy Trojan horse code. (This also affects old 3.x releases before 3.5.) NOTE: the vendor's position is that it is the user's responsibility to ensure C:\Python27 access control or choose a different directory, because backwards compatibility requires that C:\Python27 remain the default for 2.7.x.
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Analysis
by VulDB Data Team • 08/05/2024
The vulnerability described in CVE-2019-13404 represents a significant security concern within the Python installation process on Windows systems, specifically affecting Python versions through 2.7.16 and certain older 3.x releases prior to 3.5. This issue stems from the default installation directory configuration used by the MSI installer package, which consistently places Python components in the C:\Python27 directory structure. The fundamental security flaw lies in the assumption that default installation paths will remain secure and isolated from potential malicious interference, creating an environment where local attackers can exploit the predictable default location to deploy malicious code with elevated privileges.
The technical implementation of this vulnerability exploits the principle of least privilege and default secure configuration practices that should be inherent in software installation processes. When Python installs to the C:\Python27 directory by default, it creates a predictable attack surface that malicious actors can leverage to place Trojan horse code in a location that is already part of the system's execution path. This default installation behavior violates the security principle that software should not create easily exploitable default configurations, especially when those configurations place critical system components in locations that are accessible to local users without proper access controls. The vulnerability is particularly concerning because it affects a widely used programming language and its installation process, making it a prime target for exploitation in environments where local privilege escalation attacks are possible.
From an operational impact perspective, this vulnerability creates a substantial risk for organizations that rely on Python installations, particularly in enterprise environments where multiple users may have local access to systems. The default installation path provides attackers with a known location to target for code injection or replacement attacks, potentially leading to persistent backdoors or privilege escalation scenarios. The vulnerability affects not just individual users but entire organizational infrastructures, as the default location becomes a common attack vector across multiple systems. Security professionals must consider this weakness when evaluating system configurations and implementing access control measures, as the default installation path bypasses normal security assumptions about where critical system components should be located and how they should be protected.
The vendor's position regarding this vulnerability, as documented in the CVE entry, reflects a complex balance between backward compatibility requirements and security considerations. The assertion that it is the user's responsibility to ensure proper access controls or choose alternative directories demonstrates the tension between maintaining legacy system compatibility and implementing modern security practices. This vendor stance aligns with the concept of security through obscurity being insufficient, yet acknowledges the practical constraints of maintaining backward compatibility in widely deployed software. Organizations implementing Python on Windows systems must recognize that the default installation behavior creates a security risk that cannot be mitigated solely through user awareness, as the default configuration itself represents a security weakness. The vulnerability's impact extends beyond simple access control issues to encompass broader system integrity concerns, particularly when considering that the C:\Python27 directory may already contain system-level components that could be targeted for privilege escalation.
Mitigation strategies for this vulnerability should include explicit directory selection during installation processes, implementation of proper access controls on the default installation paths, and regular security audits to ensure that Python installations are not vulnerable to local code injection attacks. Organizations should consider using custom installation directories that are not easily guessable and implement proper file system permissions to prevent unauthorized modifications to Python installation locations. The security community should also consider this vulnerability as an example of how default configurations can create inherent security weaknesses, particularly in environments where multiple users have local access to systems. This issue highlights the importance of secure default configurations and the need for software vendors to balance compatibility requirements with security best practices. The vulnerability's classification under CWE categories related to insecure default configurations and privilege escalation demonstrates the severity of the issue and the need for proactive mitigation measures. Security frameworks such as ATT&CK should recognize this as a potential entry point for initial access and privilege escalation phases, as attackers can exploit predictable default installation paths to establish persistent access to systems.