CVE-2018-20225: Pip Package Manager Vulnerable to Dependency Confusion Through Private Index Exploitation

CVE-2018-20225 identifies a critical Python package management vulnerability in pip (all versions) that enables dependency confusion attacks through the --extra-index-url option. This vulnerability affects organizations using private Python package repositories, with an EPSS score of 76.3 percentile and 1% exploitation probability, indicating moderate but persistent attack potential. The vulnerability details reveal that pip installs packages with the highest version number regardless of the intended source, allowing attackers to hijack private packages by claiming unclaimed package names on the public PyPI repository with higher version numbers. This creates substantial exploit risk for organizations relying on private Python packages that haven't secured their package names on the public index, potentially leading to arbitrary code execution when malicious packages are installed instead of legitimate private dependencies. The technical root cause lies in pip's package resolution algorithm when using --extra-index-url, where the tool prioritizes version numbers over source repository trust, creating an attack vector for known exploited vulnerabilities through dependency confusion. The vulnerability specifically targets scenarios where private PyPI servers contain packages with names not claimed on the public PyPI, enabling attackers to publish malicious packages with higher version numbers to intercept installation attempts. This affects CBL Mariner, Linux Debian, and other systems using python3-pip components, with organizations particularly vulnerable if they use private packages without claiming corresponding names on public repositories. Mitigation steps include using --index-url instead of --extra-index-url, implementing version-pinning and hash-pinning for deployments, and proactively claiming private package names on the public PyPI to prevent hijacking. Organizations should audit their private Python dependencies, implement strict package source controls, and maintain updated CVE database records to track similar supply chain vulnerabilities that could compromise software development and deployment pipelines.