CVE-2019-9636 Explained : Impact and Mitigation

Python versions 2.7.x through 2.7.16 and 3.x through 3.7.2 are affected by a vulnerability due to improper handling of Unicode encoding during NFKC normalization. This can lead to the disclosure of sensitive information like credentials and cookies.

Understanding CVE-2019-9636

This CVE involves a vulnerability in Python versions 2.7.x through 2.7.16 and 3.x through 3.7.2 related to Unicode encoding during NFKC normalization.

What is CVE-2019-9636?

The vulnerability arises from the mishandling of Unicode encoding during NFKC normalization, particularly when an incorrect netloc is involved. Attackers can exploit this flaw to reveal sensitive data cached against a specific hostname.

The Impact of CVE-2019-9636

Disclosure of sensitive information such as credentials and cookies
Vulnerable components: urllib.parse.urlsplit and urllib.parse.urlparse
Attackers can craft URLs to extract and send information to a different host

Technical Details of CVE-2019-9636

This section provides more in-depth technical insights into the vulnerability.

Vulnerability Description

The vulnerability in Python versions 2.7.x through 2.7.16 and 3.x through 3.7.2 stems from improper handling of Unicode encoding during NFKC normalization.

Affected Systems and Versions

Python versions 2.7.x through 2.7.16
Python versions 3.x through 3.7.2

Exploitation Mechanism

Attackers can exploit this vulnerability by creating specially crafted URLs that are incorrectly parsed, allowing them to access and transmit sensitive information to unauthorized hosts.

Mitigation and Prevention

Protecting systems from CVE-2019-9636 requires immediate actions and long-term security practices.

Immediate Steps to Take

Update Python to the fixed versions: v2.7.17, v2.7.18, v3.5.10, v3.6.10, v3.7.3, and later
Monitor for any unusual activities related to URL parsing

Long-Term Security Practices

Regularly update Python and other software components
Implement network segmentation to limit the impact of potential breaches

Patching and Updates

Ensure timely installation of security patches and updates provided by Python and relevant vendors.