ReversingLabs researchers identified a supply chain vulnerability in legacy Python packages related to the 'distribute' module, which historically served as a packaging tool before being deprecated. The vulnerability (CVE-2023-45311) arises from bootstrap scripts embedded in affected packages that, during installation, fetch and execute an installation script from the domain python-distribute.org. This domain is no longer owned by the original maintainers and is currently available for sale, creating a domain takeover risk. If an attacker acquires this domain, they can serve malicious installation scripts to any environment running these bootstrap scripts, leading to arbitrary code execution. Affected packages include widely used Python projects such as tornado, pypiserver, and slapos.core, among others. The issue stems from the complex evolution of Python packaging tools and the failure to formally decommission the 'distribute' module, resulting in legacy code that still relies on hard-coded external domains. This scenario exemplifies the dangers of code rot and the importance of maintaining supply chain integrity in open-source ecosystems. Although no exploits have been observed in the wild, the potential impact is significant due to the trust placed in PyPI packages and the ease with which compromised installation scripts could propagate malicious code. The vulnerability is categorized as medium severity, reflecting the moderate ease of exploitation combined with the potentially broad impact on confidentiality, integrity, and availability of affected systems.

For European organizations, this vulnerability poses a significant supply chain risk. Organizations relying on Python packages such as tornado, pypiserver, and slapos.core—common in web services, internal tooling, and cloud infrastructure—may inadvertently execute malicious code if their build environments use legacy bootstrap scripts referencing python-distribute.org. This could lead to unauthorized code execution, data breaches, service disruptions, or further lateral movement within networks. The impact is amplified in sectors with critical infrastructure or sensitive data, including finance, healthcare, and government services. Since PyPI is a global repository, the risk is not geographically constrained but depends on the adoption of affected packages and legacy build processes. European entities with extensive Python development or deployment pipelines are at risk, especially if they have not audited or updated legacy dependencies. The medium severity rating reflects that while exploitation requires running vulnerable bootstrap scripts, no authentication or user interaction is needed, making automated attacks feasible in some environments. The potential for widespread compromise through supply chain poisoning underscores the need for proactive mitigation.

1. Audit all Python projects and dependencies for usage of legacy bootstrap scripts that reference python-distribute.org or the 'distribute' module. 2. Remove or replace any usage of the 'distribute' module with modern, actively maintained packaging tools such as setuptools or pip. 3. Avoid hard-coded external domains in build or installation scripts; use verified package repositories and secure URLs. 4. Implement strict supply chain security practices, including verifying package integrity via checksums and signatures. 5. Monitor for any acquisition or changes in ownership of python-distribute.org and related domains to detect potential malicious activity. 6. Update CI/CD pipelines and build environments to disallow execution of legacy bootstrap scripts or untrusted external code during package installation. 7. Engage with open-source communities to encourage deprecation and removal of legacy code that relies on vulnerable domains. 8. Educate developers and DevOps teams about supply chain risks and the importance of dependency hygiene. 9. Employ runtime detection tools to identify unexpected network calls or script executions during package installation. 10. Consider network-level controls to block access to suspicious or unowned domains referenced in build scripts.