Microsoft’s Patch Tuesday updates for February 2020 address 99 vulnerabilities, including an Internet Explorer zero-day reportedly exploited by a threat group known as DarkHotel.
Microsoft disclosed the existence of the Internet Explorer zero-day on January 17, when it promised to release patches and provided a workaround. At the time, the company noted that it would likely only fix it with its February updates.
The vulnerability, tracked as CVE-2020-0674, is caused by a memory corruption in the scripting engine used by Internet Explorer 9, 10 and 11. More precisely, the weakness exists in a library named jscript.dll, which provides compatibility with a deprecated version of the JScript scripting language.
CVE-2020-0674 can be exploited for remote code execution in the context of the targeted user. The attacker must convince the victim to visit a malicious website in order to exploit the flaw.
Microsoft has credited Google’s Threat Analysis Group and Chinese cybersecurity firm Qihoo 360 for reporting the vulnerability. While Google has not released any information about the attacks involving CVE-2020-0674, Qihoo 360 said they were carried out by the DarkHotel group, which some have linked to South Korea.
Microsoft has also patched four important-severity vulnerabilities that have been publicly disclosed before the company released fixes. These include two privilege escalation issues in Windows, an information disclosure bug affecting IE and Edge, and a secure boot bypass method.
In total, the company has patched a dozen vulnerabilities rated critical in Windows and its web browsers.
Trend Micro’s Zero Day Initiative (ZDI) has looked at Microsoft’s advisories and highlighted one vulnerability in Exchange that can be exploited for code execution by sending a specially crafted email to the target. Exploitation requires no user interaction and a successful attack can allow a hacker to take complete control of an Exchange server.
Another flaw highlighted by ZDI is a remote code execution vulnerability involving Windows link files.