CVE-2025-22153: A Critical Vulnerability in RestrictedPython

 A Critical Vulnerability in RestrictedPython

CVE-2025-22153

CVE-2025-22153 is a significant security vulnerability affecting the RestrictedPython library, which is designed to create a controlled environment for executing untrusted Python code. This vulnerability arises from a type confusion bug in the CPython interpreter, specifically in versions 3.11 through 3.13.2, that allows attackers to bypass the security measures of RestrictedPython when using try/except* clauses. The vulnerability has been assigned a CVSS score of 7.9, indicating a high severity level, and was published on January 23, 2025.

Background on RestrictedPython

RestrictedPython is a Python library that enables the safe execution of potentially harmful code by restricting access to certain functionalities within the Python language. It is commonly utilized in applications where security is critical, such as web applications and sandboxed environments. However, the vulnerability in question compromises its intended security features, potentially allowing unauthorized access to sensitive operations or data.

Vulnerability Details

The core issue with CVE-2025-22153 stems from the way the CPython interpreter handles exceptions with try/except* clauses. This flaw can lead to unauthorized access to functionalities that should be restricted by the library:

• Type Confusion: The vulnerability allows an attacker to manipulate types in a way that can bypass security checks.
• Implications: If exploited, this could result in unauthorized actions being performed within an application that relies on RestrictedPython for security.

Impact Scenarios

1. Web Application Exploit: An attacker could submit malicious code through a web interface that utilizes RestrictedPython for executing user input. If this code includes try/except* clauses, it might exploit the vulnerability to gain access to restricted operations, leading to data leakage or unauthorized modifications.
2. Sandboxed Environment Breach: In environments where RestrictedPython is used to run third-party scripts safely, an attacker could craft a script designed to exploit this vulnerability, potentially gaining access to sensitive system resources or APIs that should remain off-limits.

Mitigation and Recommendations

The vulnerability has been addressed in version 8.0 of RestrictedPython, which removes support for try/except* clauses entirely. Users and developers are strongly urged to upgrade to this version or later:

bash
pip install --upgrade restrictedpython

Workarounds

Currently, there are no effective workarounds available other than upgrading to the patched version of RestrictedPython. Users should immediately assess their applications for exposure to this vulnerability and take action accordingly.

Conclusion

CVE-2025-22153 represents a critical risk for applications utilizing RestrictedPython due to its potential for exploitation via type confusion in the CPython interpreter. The removal of try/except* support in version 8.0 is a necessary step for maintaining application integrity and security. Regular updates and vigilance are essential for safeguarding against such vulnerabilities in software development practices.