CVE-2021-20112 : Vulnerability Insights and Analysis

A stored cross-site scripting vulnerability exists in TCExam <= 14.8.1. This vulnerability allows an attacker to upload a malicious JavaScript payload, which could be triggered when another user views the file.

Understanding CVE-2021-20112

This section will provide insights into the nature of the vulnerability and its potential impact.

What is CVE-2021-20112?

CVE-2021-20112 is a stored cross-site scripting (XSS) vulnerability found in TCExam <= 14.8.1. It arises when valid files are uploaded via tce_select_mediafile.php with a filename starting with a period. In such cases, these files are rendered as text/html, allowing attackers to upload malicious payloads.

The Impact of CVE-2021-20112

The impact of this vulnerability is significant as it enables attackers to execute malicious scripts within the context of the user's session, leading to potential data theft, unauthorized actions, or further exploitation of the system.

Technical Details of CVE-2021-20112

This section delves into the specific technical aspects of the vulnerability.

Vulnerability Description

The vulnerability in TCExam <= 14.8.1 allows attackers to upload files with a period-starting name via tce_select_mediafile.php, leading to a stored XSS risk where malicious JavaScript can be executed.

Affected Systems and Versions

TCExam versions up to 14.8.1 are affected by this stored XSS vulnerability, putting systems with these versions at risk of exploitation.

Exploitation Mechanism

By uploading a file with a malicious JavaScript payload to tce_select_mediafile.php with a period-starting filename, an attacker can exploit the vulnerability by triggering the payload when accessed by another user.

Mitigation and Prevention

In this section, we outline steps to mitigate the risks associated with CVE-2021-20112 and prevent potential security breaches.

Immediate Steps to Take

Immediately updating TCExam to a patched version beyond 14.8.1 can mitigate the risk associated with this vulnerability. Additionally, monitoring file uploads via tce_select_mediafile.php can help detect any suspicious activity.

Long-Term Security Practices

In the long term, implementing secure coding practices, conducting regular security audits, and educating users on safe file upload procedures can enhance the overall security posture of the system.

Patching and Updates

Regularly applying security patches and updates provided by TCExam is crucial to address known vulnerabilities like CVE-2021-20112 and ensure the system's resilience against potential threats.