Internet Explorer Scripting Engine Memory Corruption Remote Code Execution Vulnerability (CVE-2020-0968)
Executive & SecOps Summary
SECOPS ASSESSMENTWindows client and server environments running Internet Explorer 9, 10, and 11
Remote attackers can execute arbitrary code with the privileges of the current user, potentially leading to full system compromise
Apply the official Microsoft cumulative security updates immediately, or restrict access to JScript.dll as a temporary workaround
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Apply the latest cumulative security updates provided by Microsoft. You can force the installation of specific KB updates using PowerShell.
# Install PSWindowsUpdate module and apply the cumulative update
Install-Module PSWindowsUpdate -Force -Verbose
Get-WindowsUpdate -KBArticleID KB4571687 -Install -AcceptAll -AutoReboot2. Temporary Workaround & Hardening Configuration
If patching cannot be applied immediately, restrict access to JScript.dll for both 32-bit and 64-bit architectures to mitigate the attack vector.
# Take ownership and deny read/execute permissions for JScript.dll
takeown /f '%windir%\system32\jscript.dll'
icacls '%windir%\system32\jscript.dll' /deny everyone:(F)
takeown /f '%windir%\syswow64\jscript.dll'
icacls '%windir%\syswow64\jscript.dll' /deny everyone:(F)3. Log Audit & IoC Verification Commands
Verify the current version of JScript.dll to determine if the system remains in a vulnerable state.
# Check JScript.dll file version
$jscriptPath = Join-Path $env:windir 'system32\jscript.dll'
if (Test-Path $jscriptPath) {
$fileVersion = (Get-Item $jscriptPath).VersionInfo.FileVersion
Write-Host 'Current JScript.dll Version:' $fileVersion
# Flag if the version is below the patched threshold
if ([Version]$fileVersion -lt [Version]'5.8.19041.450') {
Write-Warning 'Warning: Vulnerable JScript.dll version detected!'
} else {
Write-Host 'System is patched and secure.' -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-2020-0968) is a critical memory corruption vulnerability in the legacy scripting engine (JScript.dll) of Internet Explorer. The root cause lies in how the scripting engine handles objects in memory, specifically leading to a Use-After-Free (UAF) or Out-of-bounds Write (CWE-787) condition. When the engine performs garbage collection, it fails to properly track reference counts for certain objects, allowing an attacker to overwrite freed memory locations with controlled data.
2. Exploitation Mechanics & Attack Scenario
To exploit this vulnerability, an attacker hosts a specially crafted website containing malicious HTML and JavaScript. The attacker then lures targets to the site via phishing emails, malicious links, or malvertising campaigns. When a victim visits the site using Internet Explorer, the rendering engine processes the malicious script, manipulates the heap layout (e.g., via Heap Spraying), and triggers the UAF condition. This allows the attacker to bypass browser sandboxes and execute arbitrary shellcode within the context of the current user.
3. Infrastructure & Business Impact
This vulnerability has been actively exploited in the wild and is cataloged in CISA's Known Exploited Vulnerabilities (KEV) list. Successful exploitation grants the attacker initial access to the endpoint, which can be leveraged for lateral movement, ransomware deployment, credential harvesting, and complete domain compromise, posing severe risks to business continuity and data integrity.
Official Vendor Advisories & References
A remote code execution vulnerability exists in the way that the scripting engine handles objects in memory in Internet Explorer, aka 'Scripting Engine Memory Corruption Vulnerability'. This CVE ID is unique from CVE-2020-0970.
Frequently Asked SecOps Questions (CVE-2020-0968)
FAQQ1. How critical is CVE-2020-0968 and is it actively exploited in the wild?
CVE-2020-0968 is rated CVSS 7.5 (HIGH) with a 30-day EPSS exploitation probability of 30.7%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2020-0968?
Primary impacted vendors include microsoft across internet explorer. Scope summary: Internet Explorer 9, 10, and 11 on Windows 7, 8.1, 10, and Windows Server 2008, 2012, 2016, 2019
Q3. What temporary mitigations or workarounds exist for CVE-2020-0968 before patching?
[Mitigation] Apply the official Microsoft cumulative security updates immediately, or restrict access to JScript.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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