Microsoft Office Remote Code Execution Vulnerability (CVE-2017-0261) Security Advisory and Mitigation Guide
Executive & SecOps Summary
SECOPS ASSESSMENTMicrosoft Office 2010 SP2, Office 2013 SP1, and Office 2016.
Remote attackers can execute arbitrary code in the context of the current user and fully compromise the target system via crafted Office documents.
Apply official Microsoft security patches immediately or disable the vulnerable EPS (Encapsulated PostScript) filter via registry modification.
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Deploy the official security updates provided by Microsoft. In enterprise environments, administrators can force the installation of the required KB patches using the Windows Update PowerShell module.
# Install Windows Update module and apply relevant security patches
Install-Module PSWindowsUpdate -Force -Verbose
Get-WindowsUpdate -KBArticleID KB3191837, KB3191908, KB3191932 -Install -AcceptAll -AutoReboot2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, disable the EPS filter in the Windows Registry to mitigate the attack vector.
Windows Registry Editor Version 5.00
; Disable EPS Filter for Office 2016
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\16.0\Common\Security\AllowFlts]
'EPSIMP32.FLT'=dword:00000000
; Disable EPS Filter for Office 2013
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\15.0\Common\Security\AllowFlts]
'EPSIMP32.FLT'=dword:00000000
; Disable EPS Filter for 32-bit Office on 64-bit OS (Wow6432Node)
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Office\16.0\Common\Security\AllowFlts]
'EPSIMP32.FLT'=dword:000000003. Log Audit & IoC Verification Commands
Use the following PowerShell script to verify whether the EPS filter has been successfully disabled across the registry paths.
# Check the status of the EPS filter registry mitigation
$paths = @(
'HKLM:\SOFTWARE\Microsoft\Office\16.0\Common\Security\AllowFlts',
'HKLM:\SOFTWARE\Microsoft\Office\15.0\Common\Security\AllowFlts',
'HKLM:\SOFTWARE\Wow6432Node\Microsoft\Office\16.0\Common\Security\AllowFlts'
)
foreach ($path in $paths) {
if (Test-Path $path) {
$val = Get-ItemProperty -Path $path -Name 'EPSIMP32.FLT' -ErrorAction SilentlyContinue
if ($val -and $val.EPSIMP32.FLT -eq 0) {
Write-Host '[SAFE] EPS Filter is disabled on' $path -ForegroundColor Green
} else {
Write-Host '[WARNING] EPS Filter is NOT disabled on' $path -ForegroundColor Red
}
} else {
Write-Host '[INFO] Path not found (Office version may differ):' $path -ForegroundColor Yellow
}
}Block Kernel Privilege Escalation & Ransomware Payloads Before You Can Reboot
Protect unpatched Windows, Linux, and macOS workloads against in-memory exploitation and lateral movement with autonomous EDR.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2017-0261) is a Use-After-Free (CWE-416) vulnerability that occurs when Microsoft Office fails to properly handle objects in memory. Specifically, the flaw resides within the Encapsulated PostScript (EPS) graphics filter used by Office to parse and render EPS images embedded in documents. Improper memory management during parsing allows an attacker to reference freed memory, leading to arbitrary code execution.
2. Exploitation Mechanics & Attack Scenario
An attacker exploits this vulnerability by crafting a malicious Office document (such as .docx or .xlsx) containing an embedded, specially crafted EPS file. When a user opens the document, the Office application automatically invokes the EPS filter to render the image. This triggers the Use-After-Free condition, corrupting system memory and allowing the execution of attacker-controlled shellcode under the privileges of the logged-in user.
3. Infrastructure & Business Impact
As a high-severity vulnerability listed in the CISA KEV catalog, CVE-2017-0261 has been actively exploited in the wild by advanced persistent threat (APT) actors. Successful exploitation can lead to complete endpoint compromise, serving as an initial entry point for attackers to deploy ransomware, exfiltrate sensitive corporate data, and perform lateral movement across the internal network.
Official Vendor Advisories & References
Microsoft Office 2010 SP2, Office 2013 SP1, and Office 2016 allow a remote code execution vulnerability when the software fails to properly handle objects in memory, aka "Office Remote Code Execution Vulnerability". This CVE ID is unique from CVE-2017-0262 and CVE-2017-0281.
Frequently Asked SecOps Questions (CVE-2017-0261)
FAQQ1. How critical is CVE-2017-0261 and is it actively exploited in the wild?
CVE-2017-0261 is rated CVSS 7.8 (HIGH) with a 30-day EPSS exploitation probability of 78.1%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2017-0261?
Primary impacted vendors include microsoft across office. Scope summary: Microsoft Office 2010 Service Pack 2, Microsoft Office 2013 Service Pack 1, Microsoft Office 2016
Q3. What temporary mitigations or workarounds exist for CVE-2017-0261 before patching?
[Mitigation] Apply official Microsoft security patches immediately or disable the vulnerable EPS (Encapsulated PostScript) filter via registry modification. Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
Generate an Internal Engineering Notice or CISO Report for CVE-2017-0261
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