Microsoft Internet Explorer 6-10 Use-After-Free Remote Code Execution Vulnerability (CVE-2013-2551, MS13-037)
Executive & SecOps Summary
SECOPS ASSESSMENTMicrosoft Internet Explorer versions 6, 7, 8, 9, and 10
Remote attackers can execute arbitrary code with the privileges of the active user by enticing them to visit a specially crafted malicious website that triggers a Use-After-Free condition.
Apply the official Microsoft MS13-037 security update, transition to modern browsers (e.g., Microsoft Edge), or unregister the VML rendering engine (vgx.dll) as a temporary workaround.
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
The primary remediation is to apply the MS13-037 security update. For legacy systems, you can force the installation of the required cumulative security update via PowerShell:
# Install Windows Update module and apply the cumulative update for IE
Install-Module PSWindowsUpdate -Force -Verbose
Get-WindowsUpdate -KBArticleID KB2829628 -Install -AcceptAll -AutoReboot2. Temporary Workaround & Hardening Configuration
If patching cannot be immediately scheduled, disable the VML rendering engine (vgx.dll) to mitigate the attack vector. Run the following commands in an elevated Command Prompt:
:: Unregister the VML rendering engine DLL
regsvr32.exe /u '%CommonProgramFiles%\Microsoft Shared\VGX\vgx.dll'
:: For 64-bit systems, also unregister the 32-bit DLL
regsvr32.exe /u '%CommonProgramFiles(x86)%\Microsoft Shared\VGX\vgx.dll'3. Log Audit & IoC Verification Commands
Use the following PowerShell script to verify whether the vulnerable VML engine is registered and to check the file version of vgx.dll:
# Check the file version of vgx.dll to verify patch status
$Path = '${env:CommonProgramFiles}\Microsoft Shared\VGX\vgx.dll'
if (Test-Path $Path) {
$Version = (Get-Item $Path).VersionInfo.FileVersion
Write-Output 'Current VGX.dll Version: ' $Version
Write-Output 'Ensure this version matches or exceeds the MS13-037 patch level for your OS.'
} else {
Write-Output 'VGX.dll is not present or has been successfully removed/unregistered.'
}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 is a critical Use-After-Free (CWE-416) flaw residing within the Vector Markup Language (VML) rendering engine (vgx.dll) of Microsoft Internet Explorer. The root cause is improper object lifecycle management when processing VML elements dynamically via JavaScript. When a VML object is deleted but its reference is retained, subsequent access to this dangling pointer leads to memory corruption.
2. Exploitation Mechanics & Attack Scenario
An attacker exploits this vulnerability by hosting a malicious web page containing crafted HTML and VML code. When a vulnerable browser renders the page, the script triggers the allocation and subsequent premature deallocation of a VML object. The attacker then utilizes heap spraying techniques to populate the freed memory space with controlled data (such as a crafted virtual function table and shellcode). When the browser attempts to call a method on the deleted object, control flow is redirected to the attacker's payload, bypassing DEP and ASLR under specific conditions.
3. Infrastructure & Business Impact
Originally demonstrated by VUPEN at the CanSecWest Pwn2Own 2013 competition, this vulnerability has been actively exploited in the wild and is cataloged in the CISA KEV database. Successful exploitation grants the attacker the same user rights as the current user. If the user is logged in with administrative privileges, the attacker can compromise the entire host, install malware, exfiltrate sensitive data, and establish a persistent foothold within the enterprise network.
Official Vendor Advisories & References
Use-after-free vulnerability in Microsoft Internet Explorer 6 through 10 allows remote attackers to execute arbitrary code via a crafted web site that triggers access to a deleted object, as demonstrated by VUPEN during a Pwn2Own competition at CanSecWest 2013, aka "Internet Explorer Use After Free Vulnerability," a different vulnerability than CVE-2013-1308 and CVE-2013-1309.
Frequently Asked SecOps Questions (CVE-2013-2551)
FAQQ1. How critical is CVE-2013-2551 and is it actively exploited in the wild?
CVE-2013-2551 is rated CVSS 8.8 (HIGH) with a 30-day EPSS exploitation probability of 74.1%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2013-2551?
Primary impacted vendors include microsoft across internet_explorer. Scope summary: Microsoft Internet Explorer 6 through 10 running on Windows XP, Vista, 7, 8, and Windows Server 2003, 2008, 2012
Q3. What temporary mitigations or workarounds exist for CVE-2013-2551 before patching?
[Mitigation] Apply the official Microsoft MS13-037 security update, transition to modern browsers (e.g., Microsoft Edge), or unregister the VML rendering engine (vgx.dll) as a temporary workaround. Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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