It’s Patch Tuesday again. Microsoft is addressing fewer individual vulnerabilities this month than last, but there’s still plenty to keep admins and defenders occupied.
Three zero-day vulnerabilities are vying for your attention today: a lone Microsoft Publisher vulnerability as well as a couple affecting Windows itself. None is marked as publicly disclosed, but Microsoft has already observed in-the-wild exploitation of all three.
One zero-day vulnerability is a Security Features Bypass vulnerability in Microsoft Publisher. Successful exploitation of CVE-2023-21715 allows an attacker to bypass Office macro defenses using a specially-crafted document and run code which would otherwise be blocked by policy. Only Publisher installations delivered as part of Microsoft 365 Apps for Enterprise are listed as affected.
CVE-2023-23376 describes a vulnerability in the Windows Common Log File System Driver which allows Local Privilege Escalation (LPE) to SYSTEM. Although Microsoft isn’t necessarily aware of mature exploit code at time of publication, this is worth patching at the first opportunity, since it affects essentially all current Windows hosts.
CVE-2023-21823 is described as a Remote Code Execution (RCE) vulnerability in Windows Graphics Component, but has Attack Vector listed as Local. This apparent inconsistency is often accompanied with a clarification like: “The word Remote in the title refers to the location of the attacker. [...] The attack itself is carried out locally.” No such clarification is available in this case, but this is likely applicable here also. Microsoft also notes the existence of mature exploit code.
Microsoft is also releasing patches for nine critical RCE vulnerabilities. A more varied selection than last month, February 2023 includes critical RCE in an SQL Server ODBC driver, the iSCSI Discovery Service, .NET/Visual Studio, three in network authentication framework PEAP, one in Word, and two in Visual Studio only. Microsoft has not observed in-the-wild exploitation for any of these vulnerabilities, nor is any of them marked as publicly disclosed. Microsoft predicts that most of these are less likely to be exploited, with the exception of the PEAP vulnerabilities.
SharePoint Server makes another appearance today with CVE-2023-21717, which allows an authenticated user with the Manage List permission to achieve RCE. Admins responsible for a SharePoint Server 2013 instance may be interested in the FAQ, which includes what Microsoft optimistically describes as a clarification of the existing servicing model for SharePoint Server 2013.
This is the first Patch Tuesday after the end of Extended Security Updates (ESU) for Windows 8.1. Admins responsible for Windows Server 2008 instances should note that ESU for Windows Server 2008 is now only available for instances hosted in Azure or on-premises instances hosted via Azure Stack. Instances of Windows Server 2008 hosted in a non-Azure context will no longer receive security updates, so will forever remain vulnerable to any new vulnerabilities, including the two zero-days covered above.
Lead Software Engineer focusing on Vulnerability Risk Management – I help ensure that Rapid7's customers receive timely, accurate, and relevant security content.
