CVE-2021-25830 : What You Need to Know

A file extension handling issue in the [core] module of ONLYOFFICE DocumentServer versions v4.2.0.236 to v5.6.4.13 allows an attacker to achieve remote code execution by converting a crafted file from DOCT into DOCX format.

Understanding CVE-2021-25830

This CVE highlights a critical vulnerability in ONLYOFFICE DocumentServer that can be exploited by chaining multiple bugs related to improper string handling.

What is CVE-2021-25830?

The vulnerability in the [core] module of ONLYOFFICE DocumentServer versions v4.2.0.236 to v5.6.4.13 allows attackers to remotely execute code by manipulating file extensions during conversion.

The Impact of CVE-2021-25830

An attacker exploiting this vulnerability can potentially execute arbitrary code on the DocumentServer, leading to unauthorized access and control over sensitive data.

Technical Details of CVE-2021-25830

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

Vulnerability Description

The vulnerability arises from improper handling of file extensions in the [core] module of ONLYOFFICE DocumentServer, enabling attackers to trigger remote code execution when converting files.

Affected Systems and Versions

ONLYOFFICE DocumentServer versions v4.2.0.236 to v5.6.4.13 are affected by this vulnerability, exposing systems running these versions to exploitation.

Exploitation Mechanism

Attackers can exploit this vulnerability by initiating the conversion of a maliciously crafted file from DOCT to DOCX, leveraging flaws in string handling to achieve remote code execution.

Mitigation and Prevention

Protecting systems from CVE-2021-25830 requires immediate action and the implementation of robust security measures.

Immediate Steps to Take

Update ONLYOFFICE DocumentServer to the latest version to patch the vulnerability
Implement strict file validation checks and sanitization processes

Long-Term Security Practices

Regularly monitor for security updates and patches from ONLYOFFICE
Conduct security audits and penetration testing to identify and mitigate potential vulnerabilities

Patching and Updates

Stay informed about security advisories from ONLYOFFICE and promptly apply patches to ensure systems are protected against known vulnerabilities.