CVE-2021-28931 Explained : Impact and Mitigation

This article discusses the Arbitrary file upload vulnerability in Fork CMS 5.9.2 that allows attackers to create or replace arbitrary files in the /themes directory via a crafted zip file uploaded to the Themes panel.

Understanding CVE-2021-28931

This section provides insights into the impact, technical details, and mitigation strategies related to the Arbitrary file upload vulnerability in Fork CMS 5.9.2.

What is CVE-2021-28931?

CVE-2021-28931 is an Arbitrary file upload vulnerability in Fork CMS 5.9.2 that enables malicious actors to manipulate files within the /themes directory by uploading a specially crafted zip file via the Themes panel.

The Impact of CVE-2021-28931

The vulnerability poses a significant security risk as it allows unauthorized individuals to create or replace critical files within the CMS directory, potentially leading to unauthorized access, data breaches, or system compromise.

Technical Details of CVE-2021-28931

This section delves into the vulnerability description, affected systems, versions, and the exploitation mechanism.

Vulnerability Description

The vulnerability arises from insufficient validation of user-uploaded zip files in the Themes panel, enabling attackers to upload malicious files into the /themes directory.

Affected Systems and Versions

Fork CMS 5.9.2 is affected by this vulnerability, putting all instances of this version at risk of exploitation.

Exploitation Mechanism

By uploading a specifically crafted zip file to the Themes panel, threat actors can abuse the lack of proper input validation to execute arbitrary file uploads within the /themes directory.

Mitigation and Prevention

In this section, we highlight immediate steps to take and long-term security practices to mitigate the risks posed by CVE-2021-28931.

Immediate Steps to Take

Users should update Fork CMS to a fixed version that addresses the arbitrary file upload vulnerability.
Restrict access to the Themes panel to authorized personnel only.

Long-Term Security Practices

Regularly monitor and audit user uploads within the CMS to detect any anomalies or suspicious activities.
Educate users on secure file upload practices and the importance of validating files before execution.

Patching and Updates

Stay informed about security patches and updates released by Fork CMS to address vulnerabilities and enhance the platform's security posture.