Python JSON Logger Vulnerability (CVE-2025-27607) Exposes Users to RCE Risk – PoC Released

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A newly identified vulnerability, CVE-2025-27607, has brought attention to the importance of supply chain security in open-source projects. Affecting versions 3.2.0 and 3.2.1 of the widely used python-json-logger package, this flaw allows for remote code execution (RCE) under specific conditions. A proof-of-concept (PoC) has already been released by the security researcher who discovered it.

What Is CVE-2025-27607?

This vulnerability is linked to a missing development dependency, msgspec-python313-pre, which was referenced in the package configuration but had been removed from PyPI. Because of that, the name was left available for potential hijacking.

A threat actor could register a package with the same name and publish a malicious version, which unsuspecting developers could download when installing development dependencies for python-json-logger.

Technical Details

  • Weakness: CWE-829 – Inclusion of Functionality from Untrusted Control Sphere
  • Severity: Initially High (CVSS 3.1 score: 8.8), later downgraded to Low
  • Affected Versions: 3.2.0 and 3.2.1
  • Patched Version: 3.3.0

Proof of Concept (PoC) Demonstrates Exploitability

Security researcher @omnigodz discovered and demonstrated the vulnerability during a supply chain security experiment. They temporarily published the missing dependency on PyPI to simulate an exploit scenario — but did not weaponize it. The published package has since been removed, and PyPI admins have blocked the name to avoid future abuse.

The PoC shows how easily such oversights can open doors for attackers to insert arbitrary malicious code into development environments.

Why This Matters

The python-json-logger package is downloaded over 46 million times per month, making this vulnerability especially concerning. Even though the vulnerability only affects users installing the [dev] extras in Python 3.13.x, it highlights a critical blind spot in open-source development: the trust model for dependencies.

If successfully exploited, this vulnerability could allow for:

  • Silent malware installation
  • Data theft
  • System compromise through arbitrary code execution

How to Stay Safe

To protect your environment:

  • Update immediately to version 3.3.0 or higher
  • Avoid using unverified [dev] dependencies in production environments
  • Regularly audit your dependency tree using tools like pip-audit, Bandit, or Safety
  • Use trusted sources and verified maintainers when installing development tools

Final Thoughts

Even though CVE-2025-27607 was responsibly disclosed and resolved without real-world attacks, it serves as a powerful reminder that open-source supply chains are vulnerable to subtle yet serious threats.

As a developer or security professional, adopting a privacy-by-design and security-first mindset can help mitigate risks before they impact your project or organization.

References:

Divya. (2025, April 7). Python JSON logger vulnerability enables remote code execution – POC released. GBHackers Security | #1 Globally Trusted Cyber Security News Platform. https://gbhackers.com/python-json-logger-vulnerability/#google_vignette