CVE-2020-0968: Microsoft Internet Explorer Scripting Engine Memory Corruption Vulnerability

CVE-2020-0968 is a memory corruption vulnerability in the Scripting Engine of Microsoft Internet Explorer. It arises from how the engine handles objects in memory and can allow an attacker to achieve remote code execution. For IT and security teams, this matters because Internet Explorer has long been embedded in Windows environments and enterprise workflows; successful abuse can give an attacker a foothold on the endpoint running the browser.

Public detail is limited to the class of flaw and the vendor’s guidance. Confirm exact affected builds, patch identifiers, and any configuration caveats directly against the Microsoft advisory before acting.

How it works

The weakness is classified as CWE-787 (out-of-bounds write). In broad terms for this vulnerability class, the Scripting Engine mishandles objects in memory so that a write operation can occur outside the intended bounds. An attacker who can cause the engine to process specially crafted content—typically delivered through a web page or other content that Internet Explorer will render—may corrupt memory in a way that leads to arbitrary code execution in the context of the logged-on user.

No exploit mechanics, proof-of-concept details, or specific trigger conditions beyond the CISA summary are provided here. Treat any public exploit claims as unverified until you validate them against the vendor advisory and your own testing. The practical outcome of successful exploitation is remote code execution on the host running Internet Explorer.

Am I affected? How to find it in your systems

Internet Explorer historically shipped with Windows and may still be present even on systems that primarily use other browsers. It can appear as a standalone browser, as a rendering component inside other applications, or via compatibility modes and enterprise group-policy settings that still invoke the Trident/MSHTML engine.

• Inventory endpoints for the presence of Internet Explorer and related scripting-engine components using your software asset management, SCCM/ConfigMgr, Intune, or equivalent discovery tools.
• Check installed Windows updates and Internet Explorer version information against the list of fixed builds in the Microsoft security advisory for CVE-2020-0968; do not rely on version numbers from secondary sources.
• Review group policy and application compatibility settings that force or allow IE rendering for intranet or line-of-business sites.
• For exploitation signs, look for unexpected Internet Explorer or related process crashes, anomalous child processes spawned from IE, unusual network connections initiated by the browser process, and endpoint-detection alerts tied to memory-corruption or script-engine behavior. Correlate with web-proxy and DNS logs for visits to untrusted or newly registered domains around the time of any crash or alert.

If your inventory tools cannot clearly identify the component, treat systems that still have Internet Explorer enabled or that host applications embedding the engine as in-scope until the advisory confirms otherwise.

How to remediate

Patch first. Apply the updates Microsoft released for this vulnerability exactly as described in the vendor advisory. CISA’s required action is to apply updates per vendor instructions; follow that guidance and verify installation through your patch-management reporting.

• Prioritize systems that still run or embed Internet Explorer, especially those used by high-privilege users or that have broad network access.
• After patching, validate that the expected security update is present and that the scripting engine is no longer at a vulnerable revision.
• Where feasible, reduce reliance on Internet Explorer by migrating sites and applications to modern, supported browsers and by disabling IE as a default handler once compatibility testing is complete.
• Harden remaining use: enforce least privilege for users, enable exploit-mitigation features already present on the OS (for example, those that constrain memory corruption), and keep endpoint detection and response coverage current.

Confirm every version, KB, and configuration recommendation against the official Microsoft advisory; do not assume applicability from generic Internet Explorer guidance.

If you can't patch immediately

Until the vendor update can be deployed, reduce exposure with compensating controls appropriate to a browser scripting-engine memory-corruption flaw.

• Segment and restrict: limit which hosts may run Internet Explorer, and isolate those hosts from sensitive networks and high-value assets.
• Disable or constrain the affected feature where business needs allow—block or tightly control use of Internet Explorer, remove it from the default browser list, and prevent automatic rendering of untrusted content in IE.
• Virtual patching / web filtering: use a web application firewall, secure web gateway, or proxy policies to block known malicious URLs and to inspect or restrict active content that would be processed by the scripting engine. Rules should be tuned to the class of attack (drive-by or crafted web content) rather than to invented signatures.
• Monitoring: increase logging and alerting on IE process creation, crashes, and outbound connections; feed these into your SIEM or EDR for rapid triage.
• User and application controls: enforce application allow-listing where practical and remind users not to browse untrusted sites with Internet Explorer.

These measures lower likelihood and impact but do not replace the vendor patch. Schedule the update as soon as operationally possible.

If your data may have been exposed

Actively exploited remote-code-execution vulnerabilities in browsers can lead to endpoint compromise and subsequent data theft or lateral movement. Known ransomware use of this specific CVE is not documented in the provided facts; still treat any confirmed exploitation as a potential incident. Follow your incident-response process: isolate affected hosts, preserve forensic evidence, reset credentials that may have been exposed, and assess whether sensitive data left the environment. As a quick additional check, you can run a free exposure scan of your email addresses against known breach datasets to see whether associated credentials or personal data have appeared in prior breaches, then force password changes and enable multi-factor authentication where needed.