Microsoft’s May 2023 security updates have addressed a total of 40 vulnerabilities, including two zero-day flaws that were actively exploited in attacks. The vulnerabilities impact various Microsoft products such as Windows, Office, Microsoft Edge, SharePoint Server, Visual Studio, SysInternals, and Microsoft Teams.
Among the vulnerabilities addressed, seven are rated Critical and 31 are rated Important in severity. The two actively exploited zero-day vulnerabilities include a Win32k elevation of privilege vulnerability (CVE-2023-29336) and a Secure Boot security feature bypass vulnerability (CVE-2023-24932).
The Win32k vulnerability allows attackers to gain SYSTEM privileges and spread malware, while the Secure Boot vulnerability enables an attacker with physical or administrative access to install an affected boot policy and bypass Secure Boot. Threat actors were observed exploiting the latter flaw to install the BlackLotus UEFI bootkit.
In addition, Microsoft addressed other severe vulnerabilities, including a Windows Network File System Remote Code Execution vulnerability (CVE-2023-24941) and a Windows Pragmatic General Multicast (PGM) Remote Code Execution vulnerability (CVE-2023-24943). Furthermore, a remote code execution flaw in SharePoint Server (CVE-2023-24955) was also patched, which was demonstrated during the Pwn2Own Vancouver 2023 exploit contest.
