CVE-2023-45139 : Exploit Details and Defense Strategies

fontTools is a library for manipulating fonts, written in Python. The subsetting module has a XML External Entity Injection (XXE) vulnerability which allows an attacker to resolve arbitrary entities when a candidate font (OT-SVG fonts), which contains a SVG table, is parsed. This allows attackers to include arbitrary files from the filesystem fontTools is running on or make web requests from the host system. This vulnerability has been patched in version 4.43.0.

Understanding CVE-2023-45139

What is CVE-2023-45139?

The CVE-2023-45139 is an XML External Entity Injection (XXE) vulnerability in the fontTools library, enabling attackers to exploit arbitrary file inclusion or make web requests.

The Impact of CVE-2023-45139

This vulnerability has a high severity rating with a CVSS base score of 7.5, affecting confidentiality by allowing arbitrary file access and potential web requests.

Technical Details of CVE-2023-45139

Vulnerability Description

The vulnerability in the fontTools library arises from improper restriction of XML External Entity Reference, leading to the XXE vulnerability.

Affected Systems and Versions

The affected system is fontTools library versions greater than or equal to 4.28.2 and less than 4.43.0.

Exploitation Mechanism

The exploit involves parsing a candidate font (OT-SVG fonts) containing an SVG table, enabling the resolution of arbitrary entities by the attacker.

Mitigation and Prevention

Immediate Steps to Take

Users are advised to update fontTools to version 4.43.0 or newer to mitigate the XXE vulnerability and prevent exploitation.

Long-Term Security Practices

Regularly monitor security advisories for fontTools library and apply patches promptly to prevent potential security breaches.

Patching and Updates

Stay informed about fontTools security releases and promptly apply updates to ensure the library is not exposed to known vulnerabilities.