CVE-2022-24473: Microsoft Excel RCE Vulnerability

CVE-2022-24473 Overview

CVE-2022-24473 is a Remote Code Execution vulnerability affecting Microsoft Excel across multiple Microsoft Office products. This vulnerability allows an attacker to execute arbitrary code on a target system when a user opens a specially crafted Excel file. The attack requires local access and user interaction, typically through social engineering tactics that convince a user to open a malicious document.

Critical Impact

Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code with the privileges of the current user, potentially leading to full system compromise, data theft, or installation of malware.

Affected Products

• Microsoft 365 Apps for Enterprise
• Microsoft Office 2019 for macOS
• Microsoft Office 2021 LTSC
• Microsoft Office 2021 LTSC for macOS

Discovery Timeline

• April 15, 2022 - CVE-2022-24473 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-24473

Vulnerability Analysis

This Remote Code Execution vulnerability in Microsoft Excel represents a significant security risk that enables attackers to execute malicious code through crafted spreadsheet files. The vulnerability requires user interaction—specifically, the victim must open a malicious Excel file for exploitation to occur. Once triggered, the vulnerability allows code execution with the same privileges as the current user, which could include administrative rights on poorly configured systems.

The attack surface is particularly concerning in enterprise environments where Excel files are commonly shared via email, collaboration platforms, and file shares. The local attack vector combined with no privilege requirements makes this an attractive target for spear-phishing campaigns and targeted attacks against organizations.

Root Cause

While Microsoft has not disclosed specific technical details about the root cause (classified as NVD-CWE-noinfo), Remote Code Execution vulnerabilities in document processing applications like Excel typically stem from memory corruption issues during file parsing, improper input validation of embedded objects, or unsafe handling of macros and embedded content. The vulnerability likely involves improper processing of specific Excel file structures or embedded components.

Attack Vector

The attack vector for CVE-2022-24473 is local, requiring an attacker to deliver a malicious Excel file to the victim. Common delivery methods include:

• Phishing emails with malicious Excel attachments
• Compromised file shares or collaboration platforms
• Drive-by downloads from malicious websites
• USB-based delivery in targeted attacks

The vulnerability requires user interaction—the victim must open the malicious file for the exploit to trigger. No special privileges are required, and the attack complexity is low, making this vulnerability relatively easy to exploit once the malicious file reaches the target.

The exploitation mechanism involves crafting a specially malformed Excel file that, when opened, triggers the vulnerability and executes attacker-controlled code. See the Microsoft Security Update Guide for additional technical details.

Detection Methods for CVE-2022-24473

Indicators of Compromise

• Unusual Excel processes spawning child processes such as cmd.exe, powershell.exe, or other shell interpreters
• Excel files with suspicious embedded objects or unusual file structures
• Network connections initiated by Excel processes to unknown external hosts
• Unexpected file system modifications or registry changes following Excel file access

Detection Strategies

• Deploy endpoint detection rules to monitor for EXCEL.EXE spawning suspicious child processes
• Implement email security filtering to scan Excel attachments for malicious content
• Enable Microsoft Defender for Office 365 to detect malicious documents before delivery
• Configure SIEM rules to correlate Excel process activity with network anomalies

Monitoring Recommendations

• Enable enhanced logging for Microsoft Office applications via Group Policy
• Monitor for process creation events where the parent process is Excel and child processes are command interpreters
• Implement file integrity monitoring on critical system directories for changes following Excel file access
• Review Windows Event Logs for Application Error events (Event ID 1000) related to Excel crashes

How to Mitigate CVE-2022-24473

Immediate Actions Required

• Apply the latest security updates from Microsoft for all affected Office products immediately
• Enable Protected View and Application Guard for Office to isolate potentially malicious documents
• Educate users about the risks of opening Excel files from untrusted sources
• Implement email filtering to quarantine suspicious Excel attachments pending review

Patch Information

Microsoft has released security updates to address CVE-2022-24473. Organizations should apply the appropriate patches for their Office installations:

• Update Microsoft 365 Apps for Enterprise via the Microsoft Update service
• Update Microsoft Office 2019 and 2021 through the Mac App Store or Microsoft AutoUpdate
• Review the Microsoft Security Update Guide for specific patch versions and deployment guidance

Workarounds

• Enable Protected View for files originating from the Internet, email attachments, and untrusted locations via Group Policy or Trust Center settings
• Configure Microsoft Defender Application Guard for Office to open untrusted documents in an isolated container
• Implement strict email attachment policies to block or sandbox Excel files from external senders
• Consider using Microsoft Office Online for viewing untrusted spreadsheets instead of desktop applications

# Enable Protected View via Registry (Windows)
# Run as Administrator
reg add "HKCU\Software\Microsoft\Office\16.0\Excel\Security\ProtectedView" /v DisableInternetFilesInPV /t REG_DWORD /d 0 /f
reg add "HKCU\Software\Microsoft\Office\16.0\Excel\Security\ProtectedView" /v DisableAttachementsInPV /t REG_DWORD /d 0 /f
reg add "HKCU\Software\Microsoft\Office\16.0\Excel\Security\ProtectedView" /v DisableUnsafeLocationsInPV /t REG_DWORD /d 0 /f