Fix KB5002831, KB5002826, KB5002829 - Office 2016 Security Update Issues

The Problem

You installed the January 2026 security updates for Office 2016 and now Word crashes on open. Excel freezes when creating new documents. Outlook dies when you click the calendar. Sound familiar?

Microsoft's January 13, 2026 Patch Tuesday delivered three security updates for Office 2016 that are causing widespread issues for MSI-based installations. These updates patch critical remote code execution vulnerabilities (CVE-2026-20948, CVE-2026-20952, CVE-2026-20953) but introduce stability problems that make the apps nearly unusable.

This guide covers the affected updates, symptoms, and multiple fix methods from quick workarounds to complete remediation.

Affected Updates

KB Number	Product	CVEs Addressed
KB5002831	Excel 2016	CVE-2026-20955, CVE-2026-20957, CVE-2026-20949
KB5002826	Office 2016 (Core)	CVE-2026-20952, CVE-2026-20953, CVE-2026-20943
KB5002829	Word 2016	CVE-2026-20948

These updates apply only to MSI-based (volume license/retail) installations of Office 2016. Click-to-Run editions like Microsoft 365 are not affected.

Symptoms

After installing these updates, users report:

Word crashes immediately on launch or when opening documents
Excel freezes when creating new workbooks or accessing certain features
Outlook crashes when switching to Calendar view
Apps stop responding during spell check or typing
Event Viewer shows Event ID 1000/1001 with exception code 0xc0000005

The crashes typically occur within seconds of launching the application or performing basic operations.

Quick Diagnosis

Check if you're affected by running this in an elevated PowerShell prompt:

Get-HotFix | Where-Object {$_.HotFixID -match "KB5002831|KB5002826|KB5002829"} | Select-Object HotFixID, InstalledOn

Check Event Viewer for crash signatures:

Get-WinEvent -FilterHashtable @{LogName='Application'; Id=1000,1001} -MaxEvents 20 | Where-Object {$_.Message -match "WINWORD|EXCEL|OUTLOOK"} | Format-List TimeCreated, Message

Fix 1: Install the Companion Fix Update (Recommended)

Microsoft has a history of releasing out-of-band fixes for problematic Office updates. Check for and install the latest Office 2016 updates via Windows Update or manually download from the Microsoft Update Catalog.

Run Windows Update via PowerShell:

$UpdateSession = New-Object -ComObject Microsoft.Update.Session
$UpdateSearcher = $UpdateSession.CreateUpdateSearcher()
$SearchResult = $UpdateSearcher.Search("IsInstalled=0 AND Type='Software'")
$SearchResult.Updates | Where-Object {$_.Title -match "Office 2016"} | Select-Object Title, LastDeploymentChangeTime

If a fix update is available, install it:

Start-Process "ms-settings:windowsupdate" -Wait

Fix 2: Run Office Online Repair

The Online Repair option reinstalls Office components and often resolves update-related crashes.

Launch repair via command line:

$OfficePath = "${env:ProgramFiles}\Microsoft Office\Office16"
if (!(Test-Path $OfficePath)) { $OfficePath = "${env:ProgramFiles(x86)}\Microsoft Office\Office16" }
Start-Process "appwiz.cpl"

Then manually:

Find Microsoft Office 2016 in the list
Click Change
Select Online Repair
Click Repair and wait for completion (requires internet)

For silent repair via command line (if you have the original media):

$SetupPath = "\\server\share\Office2016\setup.exe"
Start-Process -FilePath $SetupPath -ArgumentList "/repair ProPlus /config \\server\share\Office2016\proplus.ww\config.xml" -Wait

Fix 3: Remove Problematic Updates (Temporary Workaround)

If you need Office working immediately and can accept the security risk temporarily, uninstall the problematic updates.

View installed Office updates:

Get-HotFix | Where-Object {$_.Description -eq "Update" -or $_.Description -eq "Security Update"} | Where-Object {$_.HotFixID -match "KB500"} | Sort-Object InstalledOn -Descending | Select-Object HotFixID, Description, InstalledOn

Uninstall specific updates:

wusa.exe /uninstall /kb:5002831 /quiet /norestart
wusa.exe /uninstall /kb:5002826 /quiet /norestart
wusa.exe /uninstall /kb:5002829 /quiet /norestart
Restart-Computer -Force

Hide updates to prevent reinstallation (requires PSWindowsUpdate module):

Install-Module -Name PSWindowsUpdate -Force -Scope AllUsers
Import-Module PSWindowsUpdate
Hide-WindowsUpdate -KBArticleID "KB5002831","KB5002826","KB5002829" -Confirm:$false

Fix 4: Disable COM Add-ins

Third-party COM add-ins (especially Adobe Acrobat PDFMaker) can conflict with Office updates and cause crashes.

Launch Word in Safe Mode and disable add-ins:

Start-Process "${env:ProgramFiles(x86)}\Microsoft Office\Office16\WINWORD.EXE" -ArgumentList "/safe"

Then manually:

Go to File > Options > Add-ins
At the bottom, select COM Add-ins > Go
Uncheck all add-ins
Click OK and restart Word normally

For automated add-in disable via registry:

$AddinsPath = "HKCU:\Software\Microsoft\Office\16.0\Word\Resiliency\DisabledItems"
if (!(Test-Path $AddinsPath)) { New-Item -Path $AddinsPath -Force }

$AcrobatCLSID = "{B801CA65-A1FC-11D0-85AD-444553540000}"
Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\Word\Addins\PDFMaker.OfficeAddin" -Name "LoadBehavior" -Value 0 -ErrorAction SilentlyContinue
Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\Excel\Addins\PDFMaker.OfficeAddin" -Name "LoadBehavior" -Value 0 -ErrorAction SilentlyContinue

Fix 5: Clear Office Cache and Temp Files

Corrupted cache files can cause persistent crashes even after updates are applied.

$OfficeCachePaths = @(
    "$env:LOCALAPPDATA\Microsoft\Office\16.0\OfficeFileCache",
    "$env:LOCALAPPDATA\Microsoft\Office\Spw",
    "$env:APPDATA\Microsoft\Templates\*.dotm",
    "$env:APPDATA\Microsoft\Excel\XLSTART\*",
    "$env:APPDATA\Microsoft\Word\STARTUP\*"
)

foreach ($Path in $OfficeCachePaths) {
    if (Test-Path $Path) {
        Remove-Item -Path $Path -Recurse -Force -ErrorAction SilentlyContinue
        Write-Host "Cleared: $Path"
    }
}

Reset Word's Normal.dotm template:

$NormalTemplate = "$env:APPDATA\Microsoft\Templates\Normal.dotm"
if (Test-Path $NormalTemplate) {
    $BackupPath = "$env:APPDATA\Microsoft\Templates\Normal.dotm.bak"
    Move-Item -Path $NormalTemplate -Destination $BackupPath -Force
    Write-Host "Normal.dotm backed up and reset"
}

Fix 6: Repair Office Installation via Command Line

For enterprise deployments or when the GUI repair fails:

$OfficeClickToRun = "${env:ProgramFiles}\Common Files\microsoft shared\ClickToRun\OfficeClickToRun.exe"
$OfficeMSI = "${env:ProgramFiles(x86)}\Microsoft Office\Office16"

if (Test-Path $OfficeClickToRun) {
    Write-Host "Click-to-Run detected - use Office Deployment Tool for repair"
} elseif (Test-Path $OfficeMSI) {
    Write-Host "MSI installation detected - initiating repair"
    $Installer = New-Object -ComObject WindowsInstaller.Installer
    $Products = $Installer.Products()
    foreach ($Product in $Products) {
        $ProductName = $Installer.ProductInfo($Product, "ProductName")
        if ($ProductName -match "Office.*2016") {
            Write-Host "Found: $ProductName ($Product)"
            Start-Process "msiexec.exe" -ArgumentList "/fa $Product /qn" -Wait
        }
    }
}

Fix 7: Check for Conflicting Software

Certain security software and drivers cause Office crashes after updates.

Check for known problematic software:

$ProblematicSoftware = @(
    "*Nahimic*",
    "*GigaTrust*",
    "*Trusteer*",
    "*McAfee WebAdvisor*"
)

$Installed = Get-WmiObject -Class Win32_Product | Select-Object Name
foreach ($Pattern in $ProblematicSoftware) {
    $Match = $Installed | Where-Object {$_.Name -like $Pattern}
    if ($Match) {
        Write-Host "WARNING: Found potentially conflicting software: $($Match.Name)" -ForegroundColor Yellow
    }
}

Get-WmiObject Win32_PnPSignedDriver | Where-Object {$_.DeviceName -match "Nahimic|A-Volute"} | Select-Object DeviceName, DriverVersion

Fix 8: Full Office Reinstall (Nuclear Option)

When nothing else works, a clean reinstall resolves most issues.

Export current activation info first:

cscript "${env:ProgramFiles(x86)}\Microsoft Office\Office16\OSPP.VBS" /dstatus

Uninstall Office completely using Microsoft's removal tool:

Download the Office Removal Tool from Microsoft Support
Run SetupProd_OffScrub.exe
Select Office 2016 and remove
Restart
Reinstall from original media
Run Windows Update to get current patches

Prevention: Delay Office Updates

For managed environments, delay Office updates until issues are reported and fixed.

Block specific updates via WSUS or Group Policy:

$WSUSKey = "HKLM:\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate"
if (!(Test-Path $WSUSKey)) { New-Item -Path $WSUSKey -Force }

New-ItemProperty -Path $WSUSKey -Name "ExcludeWUDriversInQualityUpdate" -Value 1 -PropertyType DWORD -Force

For standalone machines, use the PSWindowsUpdate module to hide problematic updates before they install.

Verdict

The Reality

Office 2016 reached end of extended support on October 14, 2025. Microsoft continues releasing security updates but QA testing appears minimal. These January 2026 updates follow a pattern seen with KB5002700 in April 2025, which also caused widespread crashes and required an emergency out-of-band fix (KB5002623).

Recommendations

Immediate crashes: Try Fix 4 (disable COM add-ins) first as it's the quickest
Enterprise environments: Use Fix 3 to remove updates temporarily, then deploy the fix update when available
Persistent issues: Fix 2 (Online Repair) resolves most update-related corruption
Long-term: Plan migration to Office 2021 LTSC or Microsoft 365

Final Thoughts

Microsoft's update quality for legacy Office versions continues to decline. If you're still running Office 2016 in production, expect more incidents like this. The real fix is upgrading to a supported version, but these workarounds will keep you running until that's possible.

Having Office issues in your business? Contact us for expert IT support.