Microsoft Internet Explorer CSS Use-After-Free Remote Code Execution Vulnerability (CVE-2010-3962)
Executive & SecOps Summary
SECOPS ASSESSMENTMicrosoft Internet Explorer versions 6, 7, and 8
Remote attackers can execute arbitrary code with the privileges of the active user via a specially crafted web page
Apply official cumulative security updates (MS10-090 or later), transition to modern browsers, or implement temporary workarounds
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
The primary remediation is to apply the Microsoft cumulative security update MS10-090 (or later). For legacy systems, verify the installation of the corresponding hotfix (e.g., KB2416400) using the following command:
# Check if the MS10-090 cumulative update (KB2416400) is installed
Get-HotFix | Where-Object { $_.HotFixID -eq 'KB2416400' }2. Temporary Workaround & Hardening Configuration
If patching is not immediately feasible, enforce Data Execution Prevention (DEP) using the Enhanced Mitigation Experience Toolkit (EMET) or restrict Active Scripting in the Internet Zone via the registry to mitigate the attack vector.
:: Disable Active Scripting in the Internet Zone to prevent automated exploitation
reg add 'HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3' /v '1201' /t REG_DWORD /d 3 /f3. Log Audit & IoC Verification Commands
Use the following PowerShell script to audit the installed version of Internet Explorer and identify if a vulnerable version is present on the endpoint.
# Audit Internet Explorer executable version
$iePath = 'C:\Program Files\Internet Explorer\iexplore.exe'
if (Test-Path $iePath) {
$versionInfo = (Get-Item $iePath).VersionInfo
Write-Host 'IE Version Found:' $versionInfo.ProductVersion
if ([System.Version]$versionInfo.ProductVersion -lt [System.Version]'9.0.0.0') {
Write-Warning 'VULNERABLE: Internet Explorer version is below 9.0. Apply MS10-090 or upgrade immediately.'
} else {
Write-Host 'IE version is 9.0 or higher. Ensure latest security patches are maintained.' -ForegroundColor Green
}
}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-2010-3962) is a Use-After-Free (UAF) memory corruption flaw within the Cascading Style Sheets (CSS) parsing engine of Microsoft Internet Explorer 6, 7, and 8. The root cause lies in how the browser handles CSS token sequences and the 'clip' attribute of HTML elements. When processing these elements, the browser attempts to reference an object that has already been freed from memory (referred to as an 'invalid flag reference' or 'uninitialized memory corruption'), leading to memory corruption and potential code execution.
2. Exploitation Mechanics & Attack Scenario
An attacker exploits this vulnerability by hosting a malicious website containing specially crafted CSS stylesheets and JavaScript. When a victim visits the site using a vulnerable browser, the rendering engine processes the malicious CSS 'clip' attribute, freeing a DOM object and subsequently attempting to reuse it. By leveraging heap spraying techniques, the attacker can populate the freed memory space with controlled shellcode, hijacking the browser's execution flow to run arbitrary commands under the context of the logged-in user.
3. Infrastructure & Business Impact
This vulnerability was actively exploited in the wild in targeted attacks in November 2010. Successful exploitation allows complete system compromise, enabling attackers to install malware, exfiltrate sensitive data, and establish a persistent foothold within the enterprise network. It poses a severe risk to legacy environments, such as industrial control systems (ICS) or legacy enterprise portals that still rely on older versions of Internet Explorer.
Official Vendor Advisories & References
Use-after-free vulnerability in Microsoft Internet Explorer 6, 7, and 8 allows remote attackers to execute arbitrary code via vectors related to Cascading Style Sheets (CSS) token sequences and the clip attribute, aka an "invalid flag reference" issue or "Uninitialized Memory Corruption Vulnerability," as exploited in the wild in November 2010.
Frequently Asked SecOps Questions (CVE-2010-3962)
FAQQ1. How critical is CVE-2010-3962 and is it actively exploited in the wild?
CVE-2010-3962 is rated CVSS 8.1 (HIGH) with a 30-day EPSS exploitation probability of 96.8%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2010-3962?
Primary impacted vendors include microsoft across internet_explorer. Scope summary: Microsoft Internet Explorer 6, 7, and 8 on Windows XP, Server 2003, Vista, Server 2008, and Windows 7
Q3. What temporary mitigations or workarounds exist for CVE-2010-3962 before patching?
[Mitigation] Apply official cumulative security updates (MS10-090 or later), transition to modern browsers, or implement temporary workarounds Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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