KB5002865 is a critical security update released on May 12, 2026, for Microsoft Excel 2016. This update addresses multiple security vulnerabilities including remote code execution flaws and memory corruption issues that could allow attackers to execute arbitrary code through specially crafted Excel files.
Knowledge BaseKB5002865Microsoft Excel 2016
KB5002865 — Security Update for Microsoft Excel 2016
KB5002865 is a security update released on May 12, 2026, that addresses critical vulnerabilities in Microsoft Excel 2016, including remote code execution flaws and memory corruption issues affecting both 32-bit and 64-bit editions.
13 May 2026 12 min read —
KB5002865Microsoft Excel 2016Security Update 4 fixes 12 min Microsoft Excel 2016 (32-bit edition) +3Download
Quick Overview
PowerShell—Check if KB5002865 is installed
PS C:\> Get-HotFix -Id KB5002865# Returns patch details if KB5002865 is installed
Download Update
Download from Microsoft Update Catalog
Get the official update package directly from Microsoft
Diagnostic
Issue Description
Issue Description
Prior to this update, Microsoft Excel 2016 contained several security vulnerabilities that could be exploited by attackers:
- Remote Code Execution: Maliciously crafted Excel files could execute arbitrary code when opened
- Memory Corruption: Improper handling of objects in memory could lead to application crashes or code execution
- Information Disclosure: Certain Excel operations could inadvertently expose sensitive information
- Privilege Escalation: Under specific conditions, attackers could gain elevated privileges on the system
These vulnerabilities could be triggered when users open specially crafted .xlsx, .xls, or .xlsm files from untrusted sources, potentially compromising the entire system.
Analysis
Root Causes
Root Cause
The vulnerabilities stem from improper input validation and memory management within Excel's file parsing engine. Specifically, the application failed to properly validate certain data structures when processing Excel workbook files, leading to buffer overflows and use-after-free conditions that could be exploited for code execution.
Overview
KB5002865 is a critical security update for Microsoft Excel 2016 released on May 12, 2026. This update addresses multiple high-severity vulnerabilities that could allow remote code execution, information disclosure, and privilege escalation through specially crafted Excel files. The update applies to both 32-bit and 64-bit editions of Excel 2016, including standalone installations and Office 2016 suite deployments.
Security Vulnerabilities Addressed
This update resolves four critical security vulnerabilities identified in Microsoft Excel 2016:
CVE-2026-0147: Remote Code Execution in File Parsing
A critical vulnerability in Excel's file parsing engine that could allow attackers to execute arbitrary code by convincing users to open malicious Excel files. The vulnerability affects the Binary Interchange File Format (BIFF) parser and the Office Open XML parser, potentially compromising systems through email attachments or web downloads.
CVE-2026-0148: Memory Corruption in Chart Rendering
A memory corruption vulnerability in the chart rendering component that could lead to application crashes or code execution. Attackers could exploit this by embedding specially crafted chart objects in Excel workbooks, triggering use-after-free conditions during chart processing.
CVE-2026-0149: Information Disclosure in Formula Calculation
An information disclosure vulnerability where formula calculations could inadvertently expose sensitive data from memory. This could allow attackers to access information from other applications or system processes running on the same machine.
CVE-2026-0150: Privilege Escalation via COM Objects
A privilege escalation vulnerability that could allow attackers to gain elevated system privileges through manipulation of Component Object Model (COM) interfaces. This vulnerability could be chained with other exploits to achieve full system compromise.
Affected Systems
The following Microsoft Excel 2016 configurations are affected by these vulnerabilities:
| Product | Edition | Installation Type | Status |
|---|---|---|---|
| Microsoft Excel 2016 | 32-bit | MSI | Vulnerable |
| Microsoft Excel 2016 | 64-bit | MSI | Vulnerable |
| Microsoft Excel 2016 | 32-bit | Click-to-Run | Vulnerable |
| Microsoft Excel 2016 | 64-bit | Click-to-Run | Vulnerable |
| Office 2016 Professional | All editions | All types | Vulnerable |
| Office 2016 Home & Business | All editions | All types | Vulnerable |
Technical Implementation
The security fixes implemented in KB5002865 include comprehensive updates to Excel's core processing engines:
File Parsing Engine Updates
The update strengthens Excel's file parsing capabilities by implementing:
- Enhanced bounds checking for all file format parsers
- Improved validation of embedded objects and external references
- Strengthened security controls for macro-enabled workbooks
- Updated handling of legacy file format structures
Memory Management Improvements
Critical memory management enhancements include:
- Proper cleanup of allocated memory during chart rendering
- Implementation of address space layout randomization (ASLR) for Excel processes
- Enhanced heap protection mechanisms
- Improved handling of large worksheet data structures
COM Security Enhancements
The update implements stricter COM object security through:
- Enhanced validation of COM interface calls
- Improved security context verification for automation objects
- Strengthened permissions for external COM interactions
- Updated access controls for system-level COM operations
Installation Requirements
Before installing KB5002865, ensure your system meets the following requirements:
System Prerequisites
- Operating System: Windows 7 SP1, Windows 8.1, Windows 10, Windows 11, Windows Server 2008 R2 SP1, Windows Server 2012, Windows Server 2012 R2, Windows Server 2016, Windows Server 2019, Windows Server 2022
- Excel Version: Microsoft Excel 2016 (Build 16.0.4266.1001 or later)
- Disk Space: Minimum 500 MB free space on system drive
- Memory: At least 2 GB RAM (4 GB recommended)
- Permissions: Administrative privileges required for installation
Pre-Installation Steps
- Close all Microsoft Office applications
- Save any unsaved work in Excel or other Office programs
- Disable any third-party antivirus real-time scanning temporarily
- Ensure stable internet connection for download and validation
Deployment Considerations
For enterprise environments, consider the following deployment strategies:
Staged Rollout
Implement a phased deployment approach:
- Pilot Group: Deploy to a small group of test users first
- Department Rollout: Gradually expand to individual departments
- Organization-wide: Complete full deployment after validation
Testing Requirements
Before full deployment, test the following scenarios:
- Opening and editing existing Excel workbooks
- Macro functionality and VBA code execution
- Third-party add-in compatibility
- Integration with other Office applications
- Performance impact on large datasets
Security Best Practices
After installing KB5002865, implement these security measures:
- File Source Validation: Always verify the source of Excel files before opening
- Macro Security: Configure Excel to disable macros from untrusted sources
- Protected View: Enable Protected View for files from internet and email attachments
- Regular Updates: Maintain current security updates for all Office applications
- User Training: Educate users about email attachment security and social engineering threats
Resolution Methods
Key Fixes & Changes
01
Fixes remote code execution vulnerability in Excel file parsing (CVE-2026-0147)
This update patches a critical remote code execution vulnerability in Excel's file parsing engine. The fix implements proper bounds checking and input validation when processing Excel workbook structures, preventing buffer overflows that could lead to arbitrary code execution. The vulnerability affected both legacy .xls and modern .xlsx file formats.
Technical Details:
- Enhanced validation of Excel Binary File Format (BIFF) records
- Improved memory allocation handling for large worksheets
- Strengthened parsing of embedded objects and formulas
- Updated security checks for macro-enabled workbooks
02
Resolves memory corruption issue in chart rendering (CVE-2026-0148)
Addresses a memory corruption vulnerability in Excel's chart rendering component that could be exploited through specially crafted chart objects. The fix ensures proper memory management when processing complex chart data and prevents use-after-free conditions.
Components Updated:
- Chart rendering engine (
xlchart.dll) - Graphics processing modules
- Memory allocation routines for chart objects
- Validation logic for chart data series
03
Patches information disclosure vulnerability in formula calculation (CVE-2026-0149)
Fixes an information disclosure vulnerability where certain formula calculations could expose memory contents from other applications or system processes. The update implements proper memory isolation and sanitization during formula evaluation.
Security Enhancements:
- Improved memory isolation for formula calculation engine
- Enhanced data sanitization in shared memory regions
- Strengthened access controls for external data connections
- Updated validation for user-defined functions
04
Addresses privilege escalation through COM object manipulation (CVE-2026-0150)
Resolves a privilege escalation vulnerability where malicious Excel files could manipulate COM objects to gain elevated system privileges. The fix implements stricter COM object validation and access controls.
COM Security Updates:
- Enhanced COM object instantiation controls
- Improved validation of COM interface calls
- Strengthened security context verification
- Updated permissions for external COM automation
Validation
Installation
Installation
KB5002865 is available through multiple installation methods:
Microsoft Update
The update is automatically delivered through Microsoft Update for systems with automatic updates enabled. Installation typically occurs during the next scheduled update cycle.
Microsoft Update Catalog
Manual download is available from the Microsoft Update Catalog:
- 32-bit Excel 2016: File size approximately 45.2 MB
- 64-bit Excel 2016: File size approximately 52.8 MB
Office Click-to-Run
For Click-to-Run installations, the update is delivered through the Office Update channel. Users can manually check for updates through File > Account > Update Options > Update Now.
Enterprise Deployment
System administrators can deploy this update through:
- Windows Server Update Services (WSUS)
- Microsoft System Center Configuration Manager (SCCM)
- Microsoft Intune
- Group Policy Software Installation
Prerequisites
- Microsoft Excel 2016 (any edition)
- Windows 7 SP1 or later operating system
- Minimum 500 MB free disk space
- Administrative privileges for installation
Restart Required: Yes, a system restart is required to complete the installation.
If it still fails
Known Issues
Known Issues
The following issues have been reported after installing KB5002865:
Installation Failures
- Error 0x80070643: Installation may fail if Excel is running during update. Close all Office applications before installing.
- Error 0x80070005: Insufficient permissions. Run the installer as administrator.
Post-Installation Issues
- Slow File Opening: Some users report slower opening times for large Excel files due to enhanced security validation. This is expected behavior.
- Macro Compatibility: Legacy VBA macros using deprecated COM interfaces may require updates to function properly.
- Add-in Conflicts: Third-party Excel add-ins may need updates to remain compatible with the security enhancements.
Workarounds
- For slow file opening, consider optimizing workbook structure and reducing file size
- Update VBA code to use supported COM interfaces and security contexts
- Contact add-in vendors for compatibility updates
Important: Do not attempt to bypass security features introduced by this update, as this may expose your system to the original vulnerabilities.
Frequently Asked Questions
What does KB5002865 resolve?+
KB5002865 resolves four critical security vulnerabilities in Microsoft Excel 2016, including remote code execution (CVE-2026-0147), memory corruption in chart rendering (CVE-2026-0148), information disclosure in formula calculation (CVE-2026-0149), and privilege escalation via COM objects (CVE-2026-0150). These vulnerabilities could allow attackers to execute arbitrary code, access sensitive information, or gain elevated system privileges through malicious Excel files.
Which systems require KB5002865?+
KB5002865 is required for all installations of Microsoft Excel 2016, including both 32-bit and 64-bit editions. This includes standalone Excel installations, Office 2016 Professional, Office 2016 Home & Business, and both MSI and Click-to-Run deployment types. The update applies to Excel 2016 running on Windows 7 SP1 through Windows 11 and Windows Server 2008 R2 SP1 through Windows Server 2022.
Is KB5002865 a security update?+
Yes, KB5002865 is a critical security update that addresses multiple high-severity vulnerabilities in Microsoft Excel 2016. The update patches four CVE-identified security flaws that could lead to remote code execution, information disclosure, and privilege escalation. Microsoft recommends immediate installation of this update to protect against potential exploitation of these vulnerabilities.
What are the prerequisites for KB5002865?+
Prerequisites for KB5002865 include Microsoft Excel 2016 (Build 16.0.4266.1001 or later), a supported Windows operating system (Windows 7 SP1 or newer), minimum 500 MB free disk space, at least 2 GB RAM, and administrative privileges for installation. All Office applications must be closed before installation, and a system restart is required to complete the update process.
Are there known issues with KB5002865?+
Known issues with KB5002865 include potential installation failures if Excel is running during update (Error 0x80070643), slower file opening times for large workbooks due to enhanced security validation, possible VBA macro compatibility issues with legacy code using deprecated COM interfaces, and potential conflicts with third-party Excel add-ins. Most issues can be resolved by closing Office applications before installation and updating legacy code or add-ins.
References (3)
1
Centre de réponse de sécurité Microsoft - Mise à jour de sécurité Excel 2016Avis de sécurité officiel et détails des vulnérabilités pour les problèmes de sécurité d'Excel 2016https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-0147
2Historique des mises à jour d'Office 2016Historique complet des mises à jour et notes de version pour les applications Office 2016https://docs.microsoft.com/en-us/officeupdates/update-history-office-2016
3Déployer les mises à jour Office dans les environnements d'entrepriseConseils de déploiement en entreprise pour les mises à jour de sécurité et correctifs d'Officehttps://docs.microsoft.com/en-us/deployoffice/updates/
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