CVE-2020-1380

CVE-2020-1380 is a memory corruption vulnerability (an out-of-bounds write, CWE-787) in the Microsoft Internet Explorer scripting engine that can corrupt memory when the engine processes maliciously crafted script content. It is triggered by luring a user to visit an attacker-controlled or compromised web page in Internet Explorer or in an application that invokes the IE engine, with no authentication required. Successful exploitation allows the attacker to execute arbitrary code in the context of the current user, gaining that user's privileges on the system. All installations of the affected Microsoft Internet Explorer versions are potentially exposed, with the greatest risk to legacy and enterprise Windows systems that still browse or render content with IE. The flaw is on CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating exploitation in the wild, while no public proof-of-concept is known and ransomware use is unconfirmed.

What to do: Apply Microsoft's June 2020 (or later) Windows cumulative security updates on every system running Internet Explorer, per the vendor instructions cited by CISA. Given the KEV listing (added 2021-11-03) and high EPSS (~24% 30-day exploitation probability, 98th percentile), treat this as a priority patch. Reduce attack surface by steering users to Microsoft Edge instead of IE for web browsing and auditing internal apps or legacy sites that still invoke the IE engine to render external content.