A critical vulnerability has been discovered in ‘python-json-logger’, a popular Python library used for generating JSON logs. This vulnerability could allow attackers to execute arbitrary code on systems where the library is installed.
The vulnerability, tracked as CVE-2025-27607 and assigned a CVSS score of 8.8, stems from a missing dependency called ‘msgspec-python313-pre’. This dependency, while optional, is not present on the PyPI repository, leaving it open to exploitation.
An attacker could publish a malicious package with the same name (‘msgspec-python313-pre’) to PyPI. When developers install ‘python-json-logger’ with the optional dependencies, this malicious package would be automatically installed, potentially granting the attacker remote code execution capabilities.
Impact:
- Remote Code Execution: Attackers could potentially take complete control of affected systems.
- Data Breach: Sensitive data could be accessed and stolen by attackers.
- System Disruption: Attackers could disrupt the normal operation of affected systems.
Affected Users:
The ‘python-json-logger’ package has over 43 million downloads per month, making this vulnerability a significant threat to a large number of users. Any user who installs the package with the optional dependencies in a Python 3.13.x environment is potentially at risk.
Remediation:
Developers and organizations using ‘python-json-logger’ are strongly advised to update to version 3.3.0 or later, which includes the necessary fixes.
For a detailed proof-of-concept (PoC) and technical analysis of the vulnerability, please refer to the security advisory and the research presented at the Seaside 2025 security conference.
