CVE-2021-31939 is a high-severity remote code execution vulnerability that affects Microsoft Excel and other Microsoft Office products. This vulnerability allows attackers to execute arbitrary code on a user's machine when the user opens a specially crafted file. Given the potential impact of this vulnerability, organizations should prioritize patching immediately.
The CVSS score of 7.8 indicates a high level of risk, particularly because it requires user interaction to exploit. This means that if an unsuspecting user opens a malicious file, the attacker could gain significant control over the affected system. Therefore, it is crucial for organizations to address this vulnerability in their patch management cycles.
Risk to organizations includes unauthorized access, data breaches, and disruption of business operations due to the execution of malicious code. The urgency for defenders is high, and they should take immediate action to apply the available patches.
As of the last update, there are no known public exploits or proof of concept (PoC) code available for this vulnerability, which may provide some temporary respite; however, this does not diminish the need for prompt remediation.
Vulnerability Details
The Microsoft Excel Remote Code Execution Vulnerability allows attackers to execute arbitrary code on affected systems. The CVSS score is 7.8, indicating a high severity level. The vulnerability affects various versions of Microsoft Excel, Office, and Office Online Server, specifically those prior to the vendor patch.
This vulnerability was published on June 8, 2021, and has been classified with a high CVSS score due to its potential impact on confidentiality, integrity, and availability.
Technical Analysis
The root cause of CVE-2021-31939 lies in the improper handling of files within Microsoft Excel. Attackers can exploit this vulnerability by convincing users to open a malicious Excel file, which triggers the execution of arbitrary code.
The attack vector is local, meaning that an attacker must have some level of access to the user's environment to deliver the malicious file. The attack complexity is low, as it primarily relies on user interaction, specifically opening a crafted file. No privileges are required to exploit this vulnerability, which increases its risk factor.
The potential impacts of this vulnerability include high confidentiality, integrity, and availability impacts, as the attacker could execute arbitrary code at will.
Risk & Impact Analysis
Organizations face significant risks from CVE-2021-31939, including unauthorized access to sensitive information, potential data loss, and operational disruptions due to malicious code execution. The blast radius of this vulnerability can be extensive, impacting numerous users if exploited.
Given the nature of the vulnerability and its high CVSS score, organizations should assess their exposure and prioritize remediation. The urgency is high, and it is recommended to schedule patching as soon as possible to mitigate the risks associated with this vulnerability.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The affected products include Microsoft Excel 2013, Microsoft Excel 2016, Microsoft Office 2013, Microsoft Office 2016, Microsoft Office 2019, and various versions of Microsoft 365 Apps. All versions prior to vendor patch are vulnerable.
Mitigation & Remediation
Organizations should apply the patches provided by Microsoft for CVE-2021-31939. Detailed guidance on the patching process can be found in the Microsoft Security Update Guide. In cases where immediate patching is not possible, implementing network restrictions and monitoring for unusual activity can help mitigate potential exploitation.
For additional information on security testing, organizations may consider engaging in penetration testing to assess their environment against this vulnerability.
Detection Guidance
Organizations should monitor for any unauthorized access attempts, unusual file access, or execution of unexpected scripts within Microsoft Excel and Office products. Log indicators should include file access logs and user activity logs relevant to document handling.
AppSecure Threat Intelligence Insight
CVE-2021-31939 highlights the importance of user awareness regarding the risks associated with opening unknown or untrusted files. Security teams should implement educational programs to inform users about the potential dangers of file-based attacks. Continuous monitoring and proactive security assessments are essential to identify such vulnerabilities before they can be exploited.
For further information on vulnerability management, organizations can refer to the vulnerability management program design to enhance their security posture.
Lastly, organizations should consider regularly updating their security policies and procedures based on insights from threat intelligence to stay ahead of potential risks.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
.webp)