Microsoft's January 2023 Patch Tuesday security update contains fixes for bugs in multiple products. Here's what you need to patch now.

Microsoft's first security update for 2023 contained patches for a whopping 98 vulnerabilities, including one that attackers are actively exploiting and another that is publicly known but has not been exploited yet.

Microsoft identified 11 of the vulnerabilities it disclosed today as being of "critical" severity, meaning organizations using affected products need to prioritize these flaws before addressing the other ones. It rated the remaining 87 as "Important," which is a rating the company uses to describe vulnerabilities that, if exploited, could compromise the confidentiality, integrity, or availability of user data but are often not remotely executable or requires some level of user interaction.

**Bugs in Frequently Attacked Products**

Several of the vulnerabilities in the January 2023 security update affect products that are favorite attacker targets. Five of them, for instance, impact Microsoft Exchange Server and three — including one of the most severe flaws in this month's update — are in SharePoint.

"The volume is definitely concerning, especially given the Exchange patches and SharePoint updates," says Dustin Childs, communication manager for Trend Micro's Zero Day Initiative (ZDI) which reported 25 of the bugs that Microsoft closed today. "These are common targets — and targets that often don’t get patched," he notes. "There are also updates submitted by the National Security Agency and Canada’s Communications Security Establishment. That may raise an eyebrow or two."

Multiple security researchers identified a Microsoft SharePoint Server security feature bypass vulnerability CVE-2023-21743 as one that organizations need to jump on right away because of the risk it presents. The bug allows an unauthenticated attacker to bypass authentication and make an anonymous connection to an affected SharePoint server. One complicating factor with the vulnerability for enterprise security teams is that patching alone is not sufficient to mitigate the threat it presents. In addition, they also need to trigger a SharePoint upgrade, which Microsoft has included in this month's security update to protect against exploit activity, Microsoft said.

"This is not a 'patch it and move on' sort of bug," Childs says. "To fully address this vulnerability, admins need to take additional steps as outlined in the update documentation."

**Zero-Day Bug in Windows ALPC**

Another high-priority vulnerability in the January 2023 update is CVE-2023-21674, an actively exploited bug in Windows Advanced Local Procedure Call (ALPC) that allows an attacker to elevate privileges on a compromised system. The zero-day vulnerability impacts all Windows OS versions and could allow an attacker to escape a browser sandbox and gain system level privileges, Microsoft said.

Satnam Narang, senior staff research engineer at Tenable, says that while full details of the bug are not available, it's possible that attackers likely chained the vulnerability with a flaw in a Chromium-based browser or Microsoft Edge to break out of a browser sandbox and gain full system access. 

"Because of the improvements made in browser security, traditional browser exploits by themselves are limited by sandbox technology, restricting an attacker's ability to access the underlying operating system," Narang tells Dark Reading. He says it is likely that an advanced persistent threat group discovered and exploited the vulnerability as part of a targeted attack.

Microsoft described one of the bugs it addressed this month as publicly known but not exploited. The vulnerability, tracked as CVE-2023-21549, exists on the Windows SMB Witness Service and allows an attacker to execute remote procedure call functions normally restricted to privileged accounts only. Microsoft has assigned a score of 8.8 to the vulnerability even though it has assessed the bug as less likely to be exploited.

**A Flood of Privilege-Escalation Flaws**

Two of the 25 bugs that ZDI reported — and which Microsoft patched this month — were Exchange Server elevation-of-privilege vulnerabilities (CVE-2023-21763 and CVE-2023-21764) that resulted from a failed patch for a previous elevation of privilege flaw in Exchange tracked as CVE-2022-41123. "Thanks to the use of a hard-coded path, a local attacker could load their own DLL and execute code at the level of SYSTEM," Childs says.

In total, 39 of the bugs that Microsoft addressed in its latest update enable elevation of privileges, a category of flaw that the company often has rated as being less severe than RCE bugs. This, however, does not mean that organizations can put off addressing them. "Despite their lower score, these vulnerabilities are typically seen in the early stages of an attack and blocking attackers from gaining SYSTEM or domain-level access early in the kill chain can slow down attackers," said Kev Breen, director of cyber-threat research at Immersive Labs in a statement.

Several of the elevation of privilege bugs in the January update affect the Windows Kernel. Among them are CVE-2023-21772, CVE-2023-21750, CVE-2023-21675 and CVE-2023-21773. "The potential risk from these vulnerabilities is high since they affect all devices that run any Windows OS, starting from Windows 7," security vendor Action1 said. Seven of the privilege escalation bugs have low complexity and require low privileges and no user interaction, meaning they are easy to attack, Action1 said.

Other bugs that security researchers identified as being of high priority in Microsoft's January 2023 security update include CVE-2023-21762 and CVE-2023-21745, both of which are spoofing vulnerabilities in Microsoft Exchange Server. "Email servers like Exchange are high-value targets for attackers, as they can allow an attacker to gain sensitive information through reading emails, or to facilitate Business Email Compromise style attacks," Breen said. Organizations need to be aware of the risks that such bugs preset and mitigate them, he added.

Microsoft also updated its previous guidance around the recent use of Microsoft-signed drivers in malicious campaigns by cybercriminals. The guidance now includes a block list that blocks attackers from using the compromised certificate in their environment. For their recommended actions, the company said, "Microsoft recommends that all customers install the latest Windows updates and ensure their anti-virus and endpoint detection products are up to date with the latest signatures and are enabled to prevent these attacks."

98 Patches: Microsoft Greets New Year With Zero-Day Security Fixes

Microsoft today released updates to fix nearly 100 security flaws in its Windows operating systems and other software. Highlights from the first Patch Tuesday of 2023 include a zero-day vulnerability in Windows, printer software flaws reported by the U.S. National Security Agency, and a critical Microsoft SharePoint Server bug that allows a remote, unauthenticated attacker to make an anonymous connection.

**Microsoft** today released updates to fix nearly 100 security flaws in its **Windows** operating systems and other software. Highlights from the first **Patch Tuesday** of 2023 include a zero-day vulnerability in Windows, printer software flaws reported by the **U.S. National Security Agency**, and a critical **Microsoft SharePoint Server** bug that allows a remote, unauthenticated attacker to make an anonymous connection.

At least 11 of the patches released today are rated “Critical” by Microsoft, meaning they could be exploited by malware or malcontents to seize remote control over vulnerable Windows systems with little or no help from users.

Of particular concern for organizations running **Microsoft SharePoint Server** is CVE-2023-21743. This is a Critical security bypass flaw that could allow a remote, unauthenticated attacker to make an anonymous connection to a vulnerable SharePoint server. Microsoft says this flaw is “more likely to be exploited” at some point.

But patching this bug may not be as simple as deploying Microsoft updates. **Dustin Childs**, head of threat awareness at **Trend Micro’s Zero Day Initiative**, said sysadmins need to take additional measures to be fully protected from this vulnerability.

“To fully resolve this bug, you must also trigger a SharePoint upgrade action that’s also included in this update,” Childs said. “Full details on how to do this are in the bulletin. Situations like this are why people who scream ‘Just patch it!’ show they have never actually had to patch an enterprise in the real world.”

Eighty-seven of the vulnerabilities earned Redmond’s slightly less dire “Important” severity rating. That designation describes vulnerabilities “whose exploitation could result in compromise of the confidentiality, integrity, or availability of user data, or of the integrity or availability of processing resources.”

Among the more Important bugs this month is CVE-2023-21674, which is an “elevation of privilege” weakness in most supported versions of Windows that has already been abused in active attacks.

**Satnam Narang**, senior staff research engineer at **Tenable**, said although details about the flaw were not available at the time Microsoft published its advisory on Patch Tuesday, it appears this was likely chained together with a vulnerability in a Chromium-based browser such as Google Chrome or Microsoft Edge in order to break out of a browser’s sandbox and gain full system access.

“Vulnerabilities like CVE-2023-21674 are typically the work of advanced persistent threat (APT) groups as part of targeted attacks,” Narang said. “The likelihood of future widespread exploitation of an exploit chain like this is limited due to auto-update functionality used to patch browsers.”

By the way, when was the last time you completely closed out your Web browser and restarted it? Some browsers will automatically download and install new security updates, but the protection from those updates usually only happens after you restart the browser.

Speaking of APT groups, the U.S. National Security Agency is credited with reporting CVE-2023-21678, which is another “important” vulnerability in the Windows Print Spooler software.

There have been so many vulnerabilities patched in Microsoft’s printing software over the past year (including the dastardly PrintNightmare attacks and borked patches) that KrebsOnSecurity has joked about Patch Tuesday reports being sponsored by Print Spooler. Tenable’s Narang points out that this is the third Print Spooler flaw the NSA has reported in the last year.

**Kevin Breen** at **Immersive Labs** called special attention to CVE-2023-21563, which is a security feature bypass in **BitLocker**, the data and disk encryption technology built into enterprise versions of Windows.

“For organizations that have remote users, or users that travel, this vulnerability may be of interest,” Breen said. “We rely on BitLocker and full-disk encryption tools to keep our files and data safe in the event a laptop or device is stolen. While information is light, this appears to suggest that it could be possible for an attacker to bypass this protection and gain access to the underlying operating system and its contents. If security teams are not able to apply this patch, one potential mitigation could be to ensure Remote Device Management is deployed with the ability to remotely disable and wipe assets.”

There are also two **Microsoft Exchange** vulnerabilities patched this month — CVE-2023-21762 and CVE-2023-21745. Given the rapidity with which threat actors exploit new Exchange bugs to steal corporate email and infiltrate vulnerable systems, organizations using Exchange should patch immediately. Microsoft’s advisory says these Exchange flaws are indeed “more likely to be exploited.”

**Adobe** released four patches addressing 29 flaws in **Adobe Acrobat** and **Reader**, **InDesign**, **InCopy**, and **Adobe Dimension**. The update for Reader fixes 15 bugs with eight of these being ranked Critical in severity (allowing arbitrary code execution if an affected system opened a specially crafted file).

For a more granular rundown on the updates released today, see the SANS Internet Storm Center roundup. Nearly 100 updates is a lot, and there are bound to be a few patches that cause problems for organizations and end users. When that happens, AskWoody.com usually has the lowdown.

Please consider backing up your data and/or imaging your system before applying any updates. And please sound off in the comments if you experience any problems as a result of these patches.

Microsoft Patch Tuesday, January 2023 Edition

Microsoft SharePoint Server Remote Code Execution Vulnerability. This CVE ID is unique from CVE-2023-21744.

CVE-2023-21742

Microsoft Office Remote Code Execution Vulnerability. This CVE ID is unique from CVE-2023-21734.

CVE-2023-21735

Microsoft Office Remote Code Execution Vulnerability. This CVE ID is unique from CVE-2023-21735.

CVE-2023-21734

Microsoft Office Visio Remote Code Execution Vulnerability. This CVE ID is unique from CVE-2023-21736, CVE-2023-21738.

CVE-2023-21737

Microsoft Office Visio Remote Code Execution Vulnerability. This CVE ID is unique from CVE-2023-21736, CVE-2023-21737.

CVE-2023-21738

Microsoft DWM Core Library Elevation of Privilege Vulnerability.

CVE-2023-21724

Microsoft Office Visio Remote Code Execution Vulnerability. This CVE ID is unique from CVE-2023-21737, CVE-2023-21738.

CVE-2023-21736

Microsoft SharePoint Server Remote Code Execution Vulnerability. This CVE ID is unique from CVE-2023-21742.

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