Microsoft Internet Explorer SetMouseCapture Use-After-Free Remote Code Execution Vulnerability (CVE-2013-3893)
Executive & SecOps Summary
SECOPS ASSESSMENTMicrosoft Internet Explorer versions 6 through 11
Remote attackers can execute arbitrary code with the privileges of the active user via crafted JavaScript and ms-help: protocol handlers
Apply the MS13-080 cumulative security update, or implement workarounds such as disabling hxds.dll loading
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
The primary remediation is to apply the MS13-080 cumulative security update (KB2879017). For legacy environments, Windows Update can be triggered via PowerShell:
# Force installation of the cumulative security update for Internet Explorer
Install-WindowsUpdate -KBArticleID KB2879017 -AcceptAll -AutoReboot2. Temporary Workaround & Hardening Configuration
If patching cannot be immediately deployed, prevent the loading of hxds.dll within Internet Explorer by setting the ActiveX Compatibility Kill-Bit in the registry.
:: Set Kill-Bit for hxds.dll ActiveX CLSID to prevent loading
reg add 'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{811977e3-b8be-11d2-961b-00c04f8ee257}' /v 'Compatibility Flags' /t REG_DWORD /d 1024 /f
reg add 'HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Internet Explorer\ActiveX Compatibility\{811977e3-b8be-11d2-961b-00c04f8ee257}' /v 'Compatibility Flags' /t REG_DWORD /d 1024 /f3. Log Audit & IoC Verification Commands
Administrators can verify the version of mshtml.dll to determine if the system remains unpatched and vulnerable.
# Check the file version of mshtml.dll to verify patch status
$path = 'C:\Windows\System32\mshtml.dll'
if (Test-Path $path) {
$fileVersion = (Get-Item $path).VersionInfo.FileVersion
Write-Output "Detected mshtml.dll Version: $fileVersion"
}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
A Use-After-Free (UAF) vulnerability exists in the SetMouseCapture implementation within mshtml.dll in Microsoft Internet Explorer. The root cause lies in the improper handling of objects in memory after a mouse capture event is triggered. When a specific HTML element is freed from memory but the browser retains a stale pointer to it, subsequent attempts to reference this pointer lead to memory corruption.
2. Exploitation Mechanics & Attack Scenario
An attacker exploits this vulnerability by enticing a user to visit a specially crafted malicious website. The site executes JavaScript that triggers SetMouseCapture on an element and then immediately destroys that element to free its memory space. The exploit then leverages the ms-help: protocol to force the loading of hxds.dll (Help Data Services), which assists in manipulating the heap layout. By performing heap spraying, the attacker overwrites the freed memory location with shellcode, hijacking the execution flow to run arbitrary commands.
3. Infrastructure & Business Impact
As a vulnerability listed in the CISA KEV catalog, this flaw has been actively exploited in targeted watering-hole attacks. Successful exploitation grants the attacker the same user rights as the current user. If the compromised user has administrative privileges, the attacker can gain complete control over the affected system, install unauthorized programs, exfiltrate sensitive data, and pivot deeper into the corporate network.
Official Vendor Advisories & References
Use-after-free vulnerability in the SetMouseCapture implementation in mshtml.dll in Microsoft Internet Explorer 6 through 11 allows remote attackers to execute arbitrary code via crafted JavaScript strings, as demonstrated by use of an ms-help: URL that triggers loading of hxds.dll.
Frequently Asked SecOps Questions (CVE-2013-3893)
FAQQ1. How critical is CVE-2013-3893 and is it actively exploited in the wild?
CVE-2013-3893 is rated CVSS 8.8 (HIGH) with a 30-day EPSS exploitation probability of 87.6%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2013-3893?
Primary impacted vendors include microsoft across internet explorer. Scope summary: Microsoft Internet Explorer versions 6, 7, 8, 9, 10, and 11
Q3. What temporary mitigations or workarounds exist for CVE-2013-3893 before patching?
[Mitigation] Apply the MS13-080 cumulative security update, or implement workarounds such as disabling hxds.dll loading Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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