CVE-2022-22716: Microsoft Excel Information Disclosure

CVE-2022-22716 Overview

CVE-2022-22716 is a Microsoft Excel Information Disclosure Vulnerability that affects a wide range of Microsoft Office products. This vulnerability is classified as a memory buffer boundary issue (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer) that could allow attackers to access sensitive information from local systems when a user opens a specially crafted Excel file.

Critical Impact

Successful exploitation of this vulnerability could lead to unauthorized disclosure of sensitive information stored in memory, potentially exposing confidential data, credentials, or system information to attackers.

Affected Products

• Microsoft 365 Apps (Enterprise Edition, x64 and x86)
• Microsoft Excel 2013 SP1, Excel 2016 (x64 and x86)
• Microsoft Office 2019 (Windows x64/x86 and macOS)
• Microsoft Office Long Term Servicing Channel 2021
• Microsoft Office Online Server
• Microsoft Office Web Apps 2013 SP1
• Microsoft SharePoint Server 2013 SP1 (Enterprise)

Discovery Timeline

• February 9, 2022 - CVE-2022-22716 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-22716

Vulnerability Analysis

This information disclosure vulnerability stems from improper memory buffer boundary operations within Microsoft Excel's file parsing functionality. When Excel processes a maliciously crafted spreadsheet file, it fails to properly validate memory access boundaries, potentially allowing read operations beyond the intended buffer limits. This out-of-bounds read condition can expose sensitive information that resides in adjacent memory regions.

The vulnerability requires local access and user interaction—specifically, a victim must open a malicious Excel file. Once triggered, the vulnerability provides high confidentiality impact, meaning sensitive data can be fully compromised, though it does not affect system integrity or availability.

Root Cause

The root cause of CVE-2022-22716 lies in CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer. Microsoft Excel's file parsing routines contain insufficient bounds checking when processing certain file structures. This allows read operations to access memory locations outside the designated buffer, creating an information disclosure vector. The vulnerability exists in how Excel handles memory allocation and access during document processing operations.

Attack Vector

The attack vector for this vulnerability is local, requiring an attacker to deliver a specially crafted Excel file to the victim. The attack scenario typically involves:

1. An attacker creates a malicious Excel document containing specially crafted data structures designed to trigger the out-of-bounds read condition
2. The attacker delivers this file to the victim through email attachments, shared network drives, or web downloads
3. The victim opens the malicious file in a vulnerable version of Microsoft Excel
4. Upon parsing the file, Excel accesses memory beyond intended boundaries
5. Sensitive information from memory is disclosed to the attacker

The vulnerability requires no special privileges to exploit but does require user interaction (opening the malicious file). The attack complexity is low, and the scope is unchanged, meaning the vulnerable component and impacted component are the same.

Detection Methods for CVE-2022-22716

Indicators of Compromise

• Unusual Excel process behavior including unexpected memory access patterns or crashes during file operations
• Excel files with anomalous internal structures or malformed records that may indicate exploitation attempts
• Unexpected data exfiltration following the opening of Excel documents from untrusted sources
• Memory dumps or crash reports indicating out-of-bounds read operations in Excel processes

Detection Strategies

• Deploy endpoint detection and response (EDR) solutions like SentinelOne to monitor Excel process behavior for anomalous memory access patterns
• Implement file integrity monitoring for Excel documents received from external sources
• Configure security information and event management (SIEM) rules to alert on Excel crashes or unusual process terminations
• Utilize Microsoft Defender Application Guard to isolate potentially malicious Office documents

Monitoring Recommendations

• Monitor for Excel processes with unexpected memory consumption or access patterns
• Track document sources and flag files from untrusted origins for additional scrutiny
• Implement logging for Office application crashes and correlate with document opening events
• Review Windows Event Logs for Application Error events related to EXCEL.EXE with memory access violations

How to Mitigate CVE-2022-22716

Immediate Actions Required

• Apply the latest Microsoft security updates for all affected Office products immediately
• Enable Microsoft Office Protected View to open untrusted documents in a sandboxed environment
• Restrict document downloads from untrusted sources and implement email attachment filtering
• Deploy application whitelisting to prevent execution of macros or embedded content in Office documents

Patch Information

Microsoft has released security updates to address this vulnerability. Organizations should apply the appropriate patches based on their installed Office products. The official security advisory and patch information can be found in the Microsoft Security Update Guide for CVE-2022-22716.

Affected versions requiring updates include:

• Microsoft 365 Apps for Enterprise
• Microsoft Excel 2013 SP1 and Excel 2016
• Microsoft Office 2019 for Windows and macOS
• Microsoft Office LTSC 2021
• Microsoft Office Online Server
• Microsoft Office Web Apps 2013 SP1
• Microsoft SharePoint Server 2013 SP1

Workarounds

• Enable Protected View in Microsoft Excel: File > Options > Trust Center > Trust Center Settings > Protected View, and enable all Protected View options
• Configure Microsoft Office to block documents from the Internet by enabling the "Block macros from running in Office files from the Internet" policy
• Use Microsoft Office Application Guard for Edge to open untrusted documents in an isolated container
• Implement network segmentation to limit potential data exfiltration paths if exploitation occurs

# Registry configuration to enable Protected View for all file origins
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 DisableAttachmentsInPV /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