CVE-2021-20838 : Security Advisory and Response

This article provides detailed information about CVE-2021-20838, a vulnerability in Office Server Document Converter that allows a remote unauthenticated attacker to conduct an XML External Entity (XXE) attack.

Understanding CVE-2021-20838

CVE-2021-20838 is a security vulnerability in Office Server Document Converter, affecting versions V7.2MR4 and earlier as well as V7.1MR7 and earlier. The vulnerability enables a remote unauthenticated attacker to trigger an XXE attack, potentially leading to a denial of service (DoS) by processing a malicious XML document.

What is CVE-2021-20838?

The CVE-2021-20838 vulnerability in Office Server Document Converter allows malicious actors to exploit XXE, enabling them to disrupt normal operations by leveraging specially crafted XML documents without authentication.

The Impact of CVE-2021-20838

The exploitation of CVE-2021-20838 could result in a DoS condition, interrupting the availability of the affected systems using Office Server Document Converter. As it permits unauthenticated remote attacks, sensitive information may be at risk of exposure or alteration.

Technical Details of CVE-2021-20838

Office Server Document Converter V7.2MR4 and earlier and V7.1MR7 and earlier are susceptible to an XXE vulnerability, allowing threat actors to exploit this weakness.

Vulnerability Description

The vulnerability in Office Server Document Converter is due to insufficient input validation, enabling attackers to inject malicious XML entities and disrupt the application's functionality, potentially leading to a DoS scenario.

Affected Systems and Versions

Office Server Document Converter versions V7.2MR4 and earlier and V7.1MR7 and earlier are impacted by CVE-2021-20838, exposing them to exploitation by remote attackers.

Exploitation Mechanism

By sending a specially crafted XML document to the vulnerable system, attackers can leverage XXE to manipulate the application's processing and trigger a denial of service event.

Mitigation and Prevention

To address CVE-2021-20838 and enhance security posture, immediate actions and long-term security best practices are recommended.

Immediate Steps to Take

Organizations should consider applying security updates or patches provided by Antenna House, Inc. to mitigate the vulnerability. Network segmentation and access controls can also restrict unauthorized access.

Long-Term Security Practices

Regular security assessments, code reviews, and security awareness training are essential for preventing similar vulnerabilities in the future. Implementing secure coding practices and validating XML input can also help reduce the risk of XXE attacks.

Patching and Updates

Ensure that Office Server Document Converter is updated to the latest secure version. Timely application of patches and monitoring for security advisories from the vendor can help protect systems from exploitation.