Pierluigi Paganini February 09, 2021

Microsoft February 2021 Patch Tuesday addresses 56 vulnerabilities, including a flaw that is known to be actively exploited in the wild.

Microsoft February 2021 Patch Tuesday security updates address 56 CVEs in multiple products, including Windows components, .NET Framework, Azure IoT, Azure Kubernetes Service, Microsoft Edge for Android, Exchange Server, Office and Office Services and Web Apps, Skype for Business and Lync, and Windows Defender.

Of these 56 vulnerabilities, 11 have been rated as Critical, 43 as Important, and two as Moderate in severity. Microsoft revealed that one of these flaws is known to be actively exploited in attacks in the wild, while six issues are listed as being publicly known at the time of release.

The CVE-2021-1732 zero-day is an elevation of privilege issues that resides in the Windows Win32k component. The flaw was exploited by threat actors to obtain SYSTEM-level access after gaining access to a Windows system. Microsoft did not disclose details about the attacks that exploited this flaw.

The vulnerability was reported by JinQuan, MaDongZe, TuXiaoYi, and LiHao from DBAPPSecurity Co., Ltd

Another interesting issue addressed by Microsoft with Microsoft February 2021 Patch Tuesday security updates is a Windows DNS Server Remote Code Execution vulnerability tracked as CVE-2021-24078.

“This patch fixes a bug in the Windows DNS Server that could allow remote code execution on affected systems. Fortunately, if your system is not configured to be a DNS server, it is not impacted by this bug. However, for those systems that are configured as DNS servers, this bug allows code execution in a privileged service from a remote, unauthenticated attacker.” reads the description provided by Zero Day Initiative. “This is potentially wormable, although only between DNS servers. Prioritize this update if you depend on Microsoft DNS servers.”

Microsoft also fixed a Windows TCP/IP Remote Code Execution vulnerability (CVE-2021-24074) and a .NET Core and Visual Studio Remote Code Execution vulnerability (CVE-2021-26701).

The details for the following CVE were disclosed online before the release of Microsoft February 2021 Patch Tuesday, but none of them was exploited in attacks in the wild.:

• CVE-2021-1721 – .NET Core and Visual Studio Denial of Service Vulnerability
• CVE-2021-1733 – Sysinternals PsExec Elevation of Privilege Vulnerability
• CVE-2021-26701 – .NET Core Remote Code Execution Vulnerability
• CVE-2021-1727 – Windows Installer Elevation of Privilege Vulnerability
• CVE-2021-24098 – Windows Console Driver Denial of Service Vulnerability
• CVE-2021-24106 – Windows DirectX Information Disclosure Vulnerability

“Today Microsoft released a set of fixes affecting Windows TCP/IP implementation that include two Critical Remote Code Execution (RCE) vulnerabilities (CVE-2021-24074, CVE-2021-24094) and an Important Denial of Service (DoS) vulnerability (CVE-2021-24086).” reads a blog post published by Microsoft. “The two RCE vulnerabilities are complex which make it difficult to create functional exploits, so they are not likely in the short term. We believe attackers will be able to create DoS exploits much more quickly and expect all three issues might be exploited with a DoS attack shortly after release.”

The lists of security updates released by Microsoft is available on the Security Update Guide portal:

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Pierluigi Paganini

(SecurityAffairs – hacking, Windows)

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