On May 9, 2023, Microsoft rolled out its regular monthly security update, popularly known as “Patch Tuesday”. This month’s updates have taken on significant importance, as they address three zero-day vulnerabilities, two of which have been exploited actively in the wild. In total, the May 2023 Patch Tuesday fixes 38 security flaws across various Microsoft products, demonstrating Microsoft’s commitment to providing a secure digital environment for its users.

The Importance of Patch Tuesday

For the uninitiated, “Patch Tuesday” is Microsoft’s regularly scheduled release of security updates for its various software products. Occurring on the second Tuesday of every month, these updates often include patches for vulnerabilities that hackers may potentially exploit. The importance of these updates cannot be overstated, as they help secure systems worldwide, enhancing the overall cybersecurity landscape.

Breaking Down the May 2023 Patch Tuesday

Out of the 38 vulnerabilities that were patched in this update, six are rated as critical, with 32 rated as important. The vulnerabilities can be categorized as follows:

  • Remote Code Execution (RCE) vulnerabilities: These accounted for 31.6% of the patched vulnerabilities. RCE vulnerabilities can be particularly dangerous as they can potentially allow attackers to take control of a victim’s system remotely.
  • Elevation of Privilege (EoP) vulnerabilities: This vulnerability type accounted for 21.1% of the patched flaws. EoP vulnerabilities can enable attackers to increase their privileges on a compromised system, giving them more control.
  • Information Disclosure vulnerabilities: Also representing 21.1% of the patched vulnerabilities, these flaws can potentially allow an attacker to gain access to sensitive information.

Spotlight on Zero-Day Vulnerabilities

The May 2023 Patch Tuesday addressed three zero-day vulnerabilities, two of which were actively exploited. Zero-day vulnerabilities are flaws that were unknown to those interested in patching or fixing them. The term “zero-day” refers to the fact that developers have “zero days” to fix the issue before it is potentially exploited by malicious actors.

The following zero-day vulnerabilities were addressed:

  1. CVE-2023-29336 – Win32k Elevation of Privilege Vulnerability: This flaw involves a privilege elevation issue in the Win32k Kernel driver that could give attackers system-level privileges, allowing them to take full control of the system.
  2. The second zero-day vulnerability was an Elevation of Privilege vulnerability in Microsoft Edge (Chromium-based). Crafted with a URL, this flaw could allow an attacker to obtain higher privileges on a machine.

Other Noteworthy Vulnerabilities

In addition to the zero-day vulnerabilities, Microsoft also addressed a significant Secure Boot bypass flaw. This vulnerability was being actively exploited by a threat actor to install the BlackLotus UEFI bootkit, a form of malware that resides in the system’s firmware and persists even after reboots or hard drive replacements.

Furthermore, 11 vulnerabilities were addressed in Microsoft Edge (Chromium-based), which reinforces the need for constant vigilance and regular updates even in recently developed software applications.

The Affected Software

The Patch Tuesday updates affect a wide range of Microsoft’s software line, including Windows 11 and Windows 10, Windows Server 20H2, and the latest versions of Windows 10 (21H1, 21H2, and 22H2).

The Takeaway from May 2023 Patch Tuesday

With the ever-increasing sophistication of cyberattacks, it’s crucial to take every opportunity to fortify your digital defenses. Regularly updating your software and staying informed about the latest security threats is key to this endeavor.

It is crucial to apply these updates promptly, particularly given the active exploitation of some vulnerabilities. By applying these updates, users can protect themselves from potential compromise and maintain the integrity of their systems.


Microsoft’s May 2023 Patch Tuesday has once again highlighted the importance of staying up-to-date with the latest security patches. The swift action taken by Microsoft in addressing these vulnerabilities demonstrates its commitment to ensuring a safe and secure digital ecosystem.

In a digital world, staying ahead of potential threats is essential. Always keep your software up-to-date, stay informed about the latest threats, and take action to protect your digital environment.