CVE-2021-3199 : Exploit Details and Defense Strategies

Directory traversal with remote code execution can occur in /upload in ONLYOFFICE Document Server before 5.6.3, when JWT is used, via a /.. sequence in an image upload parameter.

Understanding CVE-2021-3199

This CVE describes a vulnerability in ONLYOFFICE Document Server that could lead to directory traversal and remote code execution.

What is CVE-2021-3199?

CVE-2021-3199 is a security flaw in ONLYOFFICE Document Server versions prior to 5.6.3 that allows an attacker to perform directory traversal and execute remote code by manipulating the image upload parameter.

The Impact of CVE-2021-3199

Exploitation of this vulnerability could result in unauthorized access to sensitive information, data manipulation, and potential compromise of the affected system's integrity.

Technical Details of CVE-2021-3199

The technical aspects of CVE-2021-3199 include:

Vulnerability Description

The vulnerability arises due to improper input validation in the image upload parameter, allowing an attacker to traverse directories and execute arbitrary code remotely.

Affected Systems and Versions

ONLYOFFICE Document Server versions before 5.6.3 are affected by this vulnerability when JWT is utilized in the /upload functionality.

Exploitation Mechanism

By inserting a /.. sequence in the image upload parameter, an attacker could exploit the directory traversal vulnerability to execute malicious code remotely.

Mitigation and Prevention

To mitigate the risks associated with CVE-2021-3199, consider the following measures:

Immediate Steps to Take

Update ONLYOFFICE Document Server to version 5.6.3 or later, which includes a patch addressing this vulnerability.
Regularly monitor for any unauthorized access or suspicious activities on the server.

Long-Term Security Practices

Implement strict input validation mechanisms to prevent directory traversal attacks in web applications.
Educate users and administrators about the importance of secure coding practices and the risks associated with improper input handling.

Patching and Updates

Stay informed about security updates and patches released by ONLYOFFICE and promptly apply them to ensure the server remains protected against known vulnerabilities.