Microsoft released its monthly security update on Tuesday, disclosing 98 vulnerabilities. Of these vulnerabilities, 11 are classified as “Critical”, 87 are classified as “Important”, no vulnerability classified as “Moderate.”

According to Microsoft all “Critical“ vulnerability are either less likely or unlikely to be exploited, except of the security bypass vulnerability CVE-2023-21743 on Microsoft SharePoint Server machines. This vulnerability has a low complexity and can be easily triggered by an attacker. In a network-based attack, an unauthenticated user could make an anonymous connection to the targeted SharePoint server.

Two of the “Critical“ vulnerabilities, which Microsoft considers to be “less likely” to be exploited due to their complexity are CVE-2023-21535 and CVE-2023-21548. These are remote code execution (RCE) vulnerability in the Windows Secure Socket Tunneling Protocol (SSTP) which allow an unauthenticated attacker to send a specially crafted connection request to a RAS server, which could lead to remote code execution (RCE) on the RAS server and run unauthorized commands on the compromised system.

There are also five “Critical“ Remote Code Execution Vulnerability which affect the Windows Layer 2 Tunneling Protocol (L2TP). Successful exploitation could allow an unauthenticated attacker to execute code on RAS servers. These five vulnerabilities are CVE-2023-21543, CVE-2023-21546, CVE-2023-21555, CVE-2023-21556 and CVE-2023-21679.

The last “Critical“ vulnerability which we want to mention is CVE-2023-21730. It is a Remote Code Execution Vulnerability in the Windows Cryptographic Services. Microsoft did not released many details about the vulnerability, except that it is triggered from the network and of low complexity.

Developers are also at risk due to CVE-2023-21779 a Remote Code Execution vulnerability in Visual Studio Code flagged as “Important“. The user would have be enticed to open a malicious file in vscode. Users should never open anything that they do not know or trust to be safe.

Talos would also like to highlight 6 “Important“ vulnerabilities that Microsoft considers “more likely” to be exploited and can be used for privilege elevation.

  • CVE-2023-21532 Windows GDI Elevation of Privilege Vulnerability 
  • CVE-2023-21541 Windows Task Scheduler Elevation of Privilege Vulnerability 
  • CVE-2023-21552 Windows GDI Elevation of Privilege Vulnerability 
  • CVE-2023-21725 Microsoft Windows Defender Elevation of Privilege Vulnerability
  • CVE-2023-21726 Windows Credential Manager User Interface Elevation of Privilege Vulnerability
  • CVE-2023-21768 Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability

There are more vulnerabilities marked as “Important“ in the Microsoft advisory. This includes Microsoft Office and 3D Builder applications, a Microsoft ODBC Driver and others. A complete list of all the vulnerabilities Microsoft disclosed this month is available on its update page.

In response to these vulnerability disclosures, Talos is releasing a new Snort rule set that detects attempts to exploit some of them. Please note that additional rules may be released at a future date and current rules are subject to change pending additional information. Cisco Secure Firewall customers should use the latest update to their ruleset by updating their SRU. Open-source Snort Subscriber Rule Set customers can stay up to date by downloading the latest rule pack available for purchase on

The rules included in this release that protect against the exploitation of many of these vulnerabilities are 61060-61065. For Snort 3, the following rules are also available to protect against these vulnerabilities: 300358-300360.