CVE-2018-20406 Explained : Impact and Mitigation

Integer Overflow Vulnerability in Python

Understanding CVE-2018-20406

A vulnerability in Python versions prior to 3.7.1 due to mishandling of large LONG_BINPUT values leading to an integer overflow.

What is CVE-2018-20406?

The issue arises in the Modules/_pickle.c file in Python versions before 3.7.1 when a large LONG_BINPUT value is incorrectly handled during an attempt to resize to twice the size. While this could result in memory exhaustion, it is mainly impactful when serializing data in the order of tens or hundreds of gigabytes.

The Impact of CVE-2018-20406

The vulnerability could potentially lead to memory exhaustion, particularly in scenarios where the pickle format is used for serializing large amounts of data.

Technical Details of CVE-2018-20406

Details of the vulnerability and its implications

Vulnerability Description

The integer overflow vulnerability in Python versions prior to 3.7.1 occurs when a large LONG_BINPUT value is mishandled during an attempt to resize to twice the size.

Affected Systems and Versions

Python versions before 3.7.1 are affected by this vulnerability.
The issue has been resolved in versions: v3.4.10, v3.5.10, v3.5.7, v3.5.8, v3.5.9, v3.6.10, v3.6.11, v3.6.12, v3.6.7, v3.6.8, v3.6.9, v3.7.1, v3.7.2, v3.7.3, v3.7.4, v3.7.5, v3.7.6, v3.7.7, v3.7.8, v3.7.9.

Exploitation Mechanism

The vulnerability occurs due to mishandling of large LONG_BINPUT values during resizing attempts, leading to an integer overflow.

Mitigation and Prevention

Protecting systems from the CVE-2018-20406 vulnerability

Immediate Steps to Take

Update Python to versions 3.7.1 or later to mitigate the vulnerability.
Avoid serializing large amounts of data using the pickle format in affected versions.

Long-Term Security Practices

Regularly update Python to the latest versions to ensure all security patches are applied.
Implement secure coding practices to prevent similar vulnerabilities in the future.

Patching and Updates

Apply patches provided by Python to address the integer overflow vulnerability.