The May 2024 Security Update Review

Welcome to the second Tuesday of May. As expected, Adobe and Microsoft have released their standard bunch of security patches. Take a break from your regular activities and join us as we review the details of their latest advisories. If you’d rather watch the full video recap covering the entire release, you can check it out here:

Apple Patches for May 2024

Apple kicked off the May release cycle with a group of updates for their macOS and iOS platforms. Most notable is a fix for CVE-2024-23296 for iOS 16.7.8 and iPadOS 16.7.8. This vulnerability is a memory corruption issue in RTKit that could allow attackers to bypass kernel memory protections. The initial patch was released back in March, but Apple noted additional fixes would be coming, and here they are. This bug is reported as being under active attack, so if you’re using a device with an affected OS, make sure you get the update.

Apple also patched the Safari bug demonstrated at Pwn2Own Vancouver by Master of Pwn Winner Manfred Paul.

Adobe Patches for May 2024

For May, Adobe released eight patches addressing 37 CVEs in Adobe Acrobat and Reader, Illustrator, Substance3D Painter, Adobe Aero, Substance3D Designer, Adobe Animate, FrameMaker, and Dreamweaver. Eight of these vulnerabilities were reported through the ZDI program. The update for Reader should be the priority. It includes multiple Critical-rated bugs that are often used by malware and ransomware gangs. While none of these bugs are under active attack, it is likely some will eventually be exploited. The patch for Illustrator also addresses a couple of Critical-rated bugs that could result in arbitrary code execution. The patch for Aero (an augmented reality authoring and publishing tool) fixes a single code execution bug. Unless I’m mistaken, this is the first Adobe patch for this product.

The fix for Adobe Animate fixes eight bugs, seven of which result in Critical-rated code execution. The patch for FrameMaker also fixes several code execution bugs. These are classic open-and-own bugs that require user interaction. That’s the same for the single bug fixed in Dreamweaver. The patch for Substance 3D Painter addresses four bugs, two of which are rated Critical, while the patch for Substance 3D Designer fixes a single Important-rated memory leak.

None of the bugs fixed by Adobe this month are listed as publicly known or under active attack at the time of release. Adobe categorizes these updates as a deployment priority rating of 3.

Microsoft Patches for May 2024

This month, Microsoft released 59 CVEs in Windows and Windows Components; Office and Office Components; .NET Framework and Visual Studio; Microsoft Dynamics 365; Power BI; DHCP Server; Microsoft Edge (Chromium-based); and Windows Mobile Broadband. If you include the third-party CVEs being documented this month, the CVE count comes to 63. A total of two of these bugs came through the ZDI program. As with last month, none of the bugs disclosed at Pwn2Own Vancouver are fixed with this release. With Apple and VMware fixing the vulnerabilities reported during the event, Microsoft stands alone as the only vendor not to produce patches from the contest.

Of the new patches released today, only one is rated Critical, 57 are rated Important, and one is rated Moderate in severity. This release is roughly a third of the size of last month’s, so hopefully that’s a sign that a huge number of fixes in a single month isn’t going to be a regular occurrence.

Two of the CVEs released today are listed as under active attack, and one other is listed as publicly known at the time of the release. Microsoft doesn’t provide any indication of the volume of attacks, but the DWM Core bug appears to me to be more than a targeted attack. Let’s take a closer look at some of the more interesting updates for this month, starting with the DWM bug currently exploited in the wild:

-       CVE-2024-30051 – Windows DWM Core Library Elevation of Privilege Vulnerability
This bug allows attackers to escalate the SYSTEM on affected systems. These types of bugs are usually combined with a code execution bug to take over a target and are often used by ransomware. Microsoft credits four different groups for reporting the bug, which indicates the attacks are widespread. They also indicate the vulnerability is publicly known. Don’t wait to test and deploy this update as exploits are likely to increase now that a patch is available to reverse engineer.

-       CVE-2024-30043 – Microsoft SharePoint Server Information Disclosure Vulnerability
This vulnerability was reported to Microsoft by ZDI researcher Piotr Bazydło and represents an XML external entity injection (XXE) vulnerability in Microsoft SharePoint Server 2019. An authenticated attacker could use this bug to read local files with SharePoint Farm service account user privileges. They could also perform an HTTP-based server-side request forgery (SSRF), and – most importantly – perform NLTM relaying as the SharePoint Farm service account. Bugs like this show why info disclosure vulnerabilities shouldn’t be ignored or deprioritized.

-       CVE-2024-30033 – Windows Search Service Elevation of Privilege Vulnerability
This is another bug reported through the ZDI program and has a similar impact to the bug currently being exploited, although it manifests through a different mechanism. This is a link following bug in the Windows Search service. By creating a pseudo-symlink, an attacker could redirect a delete call to delete a different file or folder as SYSTEM. We discussed how this could be used to elevate privileges here. The delete happens when restarting the service. A low-privileged user can't restart the service directly. However, this could easily be combined with a bug that allows a low-privileged user to terminate any process by PID. After failure, the service will restart automatically, successfully triggering this vulnerability.

-       CVE-2024-30050 – Windows Mark of the Web Security Feature Bypass Vulnerability
We don’t normally detail Moderate-rated bugs, but this type of security feature bypass is quite in vogue with ransomware gangs right now. They zip their payload to bypass network and host-based defenses, they use a Mark of the Web (MotW) bypass to evade SmartScreen or Protected View in Microsoft Office. While we have no indication this bug is being actively used, we see the technique used often enough to call it out. Bugs like this one show why Moderate-rated bugs shouldn’t be ignored or deprioritized.

Here’s the full list of CVEs released by Microsoft for May 2024:

* Indicates this CVE had been released by a third party and is now being included in Microsoft releases.

† Indicates further administrative actions are required to fully address the vulnerability.

There’s just one Critical-rated bug this month, and it deals with a remote code execution (RCE) vulnerability in SharePoint server. An authenticated attacker could use this bug to execute arbitrary code in the context of the SharePoint Server. While permissions are needed for this to occur, any authorized user on the server has the needed level of permissions.

Looking at the other RCE bugs, we see a lot of vulnerabilities in rarely used protocols. The Windows Mobile Broadband driver and the Routing and Remote Access Service (RRAS) make up the bulk of this category. More notable are the two bugs in Hyper-V. One of these would allow an authenticated attacker to execute code on the host system. This would result in a guest-to-host escape, but Microsoft doesn’t indicate what level the code execution occurs on the host OS. After a couple of months with many SQL-related fixes, there’s just one this month. As with the previous bugs, you would need to connect to a malicious SQL server. The bug in Cryptographic Services requires a machine-in-the-middle (MITM) but could lead to a malicious certificate being imported onto the target system. The RCE bugs are rounded out with open-and-own style bugs in Excel and .NET and Visual Studio.

Moving on to the elevation of privilege (EoP) patches in this month’s release, almost all lead to SYSTEM-level code execution if an authenticated user runs specially crafted code. While there isn’t a lot else to say about these bugs, they are often used by attackers to take over a system when combined with a code execution bug – like the Excel bug mentioned above. They convince a user to open a specially crafted Excel document that executes the EoP and takes over the system. The lone exception to this is the bug in the Brokering File System component. The vulnerability allows attackers to gain the ability to authenticate against a remote host using the current user’s credentials. The attack could be launched from a low-privileged AppContainer, which would allow the attacker to execute code or access resources at a higher integrity level than that of the AppContainer execution environment.

We’ve already discussed the MotW security feature bypass (SFB), and the only other SFB vulnerability receiving a fix this month is the MSHTML engine. Just when you thought you were safe from Internet Explorer, the Trident engine rears its ugly head. This bug allows an unauthenticated attacker to get code execution if they can convince a user to open a malicious document. The code execution occurs in the context of the user, so this is another reminder not to log on with Admin privileges unless you absolutely need to.

There are only seven information disclosure bugs receiving fixes this month, and we’ve already covered the one in SharePoint. As usual, most of these vulnerabilities only result in info leaks consisting of unspecified memory contents. The bug in Power BI could result in the disclosing of “sensitive information,” but Microsoft doesn’t narrow down what type of “sensitive information” could be leaked. Similarly, the bug in Deployment Services could leak “file contents.” Microsoft provides no information on whether that’s any arbitrary file contents or only specific files, so your guess is as good as mine.

The May release includes four spoofing bugs. The first is a stored cross-site scripting (XSS) bug in Azure Migrate. There’s not a straightforward patch for this one. You need the latest Azure Migrate Agent and ConfigManager updates. More info on how to do that can be found here. There are two spoofing bugs in Dynamics 365, but they read more like XSS bugs. The final spoofing bug addressed this month is in the Bing search engine. An attacker could modify the content of the vulnerable link to redirect the victim to a malicious site.

There’s a single Tampering bug addressed in this release fixing a bug in Microsoft Intune Mobile Application Management. An attacker could gain sensitive information on a target device that has been rooted.

The final bugs for May are Denial-of-Service (DoS) vulnerabilities in ASP.NET, DHCP server, and Hyper-V. Unfortunately, Microsoft provides no additional information about these bugs and how they would manifest on affected systems.

There are no new advisories in this month’s release.

Looking Ahead

The next Patch Tuesday of 2024 will be on June 11, and I’ll return with details and patch analysis then. Until then, stay safe, happy patching, and may all your reboots be smooth and clean!