Watering hole attack found on popular North Korean

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.

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.

CVE-2021-26411 is a use-after-free (CWE-416) memory corruption vulnerability in Microsoft Internet Explorer's web rendering engine that can lead to remote code execution. It is triggered when a user, typically lured via a link, email, or watering-hole page, views attacker-controlled web content that corrupts memory, consistent with the CVSS profile requiring network access and user interaction. A successful attacker gains code execution in the context of the logged-on user, which in observed campaigns was chained into malware delivery (including exploit-kit payloads such as Dridex and VBA-based malware). Any Windows system that renders web content with Internet Explorer or its IE/MSHTML components (Edge is also listed among affected CPE products) is potentially affected, though specific version ranges are not provided in the source data. The flaw was exploited as a zero-day around Microsoft's March 2021 Patch Tuesday, was added to CISA KEV on 2021-11-03 with known ransomware use, and carries an 80.8% EPSS probability of exploitation within 30 days.

Do: Apply Microsoft's March 2021 cumulative security updates for Internet Explorer, or any later cumulative update, across all Windows clients and servers, prioritizing user workstations per the CISA KEV required action. Review proxy and endpoint logs for visits to compromised watering-hole sites (notably Korean-language news sites) and for follow-on malware such as Dridex, and restrict or disable IE/legacy IE-mode rendering of untrusted web content where feasible.