Microsoft Patch Tuesday July 2022: propaganda report, CSRSS EoP, RPC RCE, Edge, Azure Site Recovery

Hello everyone! Microsoft has been acting weird lately. I mean the recent publication of a propaganda report about evil Russians and how Microsoft is involved in the conflict between countries. It wouldn’t be unusual for a US government agency, NSA or CIA to publish such a report. But when a global IT vendor, which, in theory, should be more or less neutral, does this… This is a clear signal. It’s not about business anymore.

Alternative video link (for Russia): https://vk.com/video-149273431_456239096

I’ll take a closer look at this report in the next episode of the Vulnerability Management news, but for now let’s take a look at Microsoft July Patch Tuesday. Yes, the vendor is behaving strangely, but Microsoft products need to be patched. Right? At least for now. And tracking vulnerabilities is always a good thing. 🙂

On July Patch Tuesday, July 12, 84 vulnerabilities were released. Between June and July Patch Tuesdays, 15 vulnerabilities were released. This gives us 99 vulnerabilities in the report.

$ cat comments_links.txt 
Qualys|July 2022 Patch Tuesday. Microsoft Releases 84 Vulnerabilities with 4 Critical, plus 2 Microsoft Edge (Chromium-Based); Adobe Releases 4 Advisories, 27 Vulnerabilities with 18 Critical.|https://blog.qualys.com/vulnerabilities-threat-research/2022/07/12/july-2022-patch-tuesday
ZDI|The July 2022 Security Update Review|https://www.zerodayinitiative.com/blog/2022/7/12/the-july-2022-security-update-review

$ python3.8 vulristics.py --report-type "ms_patch_tuesday_extended" --mspt-year 2022 --mspt-month "July" --mspt-comments-links-path "comments_links.txt"  --rewrite-flag "True"
...
Creating Patch Tuesday profile...
MS PT Year: 2022
MS PT Month: July
MS PT Date: 2022-07-12
MS PT CVEs found: 84
Ext MS PT Date from: 2022-06-15
Ext MS PT Date to: 2022-07-11
Ext MS PT CVEs found: 15
ALL MS PT CVEs: 99
...
  • Urgent: 0
  • Critical: 1
  • High: 19
  • Medium: 78
  • Low: 1

Interestingly, in this Patch Tuesday, more than half of all vulnerabilities are EoP.

CSRSS EoP

What can I say, prioritization in Vulristics works correctly. At the top of the July Patch Tuesday list is one critical and actively exploited Elevation of Privilege in Windows CSRSS (CVE-2022-22047). This vulnerability has been widely reported in the media.

Client Server Runtime Subsystem, or csrss.exe, is a component of the Windows NT family of operating systems that provides the user mode side of the Win32 subsystem and is included in Windows NT 3.1 and later. Because most of the Win32 subsystem operations have been moved to kernel mode drivers in Windows NT 4 and later, CSRSS is mainly responsible for Win32 console handling and GUI shutdown.

CSRSS runs as a user-mode system service. When a user-mode process calls a function involving console windows, process/thread creation, or side-by-side support, instead of issuing a system call, the Win32 libraries (kernel32.dll, user32.dll, gdi32.dll) send an inter-process call to the CSRSS process which does most of the actual work without compromising the kernel.

This Elevation of Privilege vulnerability in CSRSS allows an attacker to execute code as SYSTEM, provided they can execute other code on the target. Bugs of this type are typically paired with a code execution bug, usually a specially crafted Office or Adobe document, to take over a system. These attacks often rely on macros, which is why so many were disheartened to hear Microsoft’s delay in blocking all Office macros by default.

Microsoft says this vulnerability has been exploited in the wild, though no further details have been shared. There is no public exploit yet. Two similar vulnerabilities in CSRSS (CVE-2022-22049 and CVE-2022-22026) were also fixed, likely as a result of Microsoft’s investigation into the in-the-wild exploitation of CVE-2022-22047.

RPC RCE

Remote Code Execution in Remote Procedure Call Runtime (CVE-2022-22038). Here Microsoft has a POC exploit. This July Patch Tuesday bug could allow a remote, unauthenticated attacker to exploit code on an affected system. While not specified in the bulletin, the presumption is that the code execution would occur at elevated privileges. Combine these attributes and you end up with a potentially wormable bug. Microsoft states the attack complexity is high. Additional actions by an attacker are required in order to prepare a target for successful exploitation and an attacker would need to make “repeated exploitation attempts” to take advantage of this bug, but unless you are actively blocking RPC activity, you may not see these attempts.

Microsoft Edge Memory Corruption

Between June and July Patch Tuesday, Memory Corruption in Microsoft Edge (CVE-2022-2294) was released. Heap buffer overflow in WebRTC, to be precise. WebRTC (Web Real-Time Communication) is a free and open-source project providing web browsers and mobile applications with real-time communication (RTC) via application programming interfaces (APIs). It allows audio and video communication to work inside web pages by allowing direct peer-to-peer communication, eliminating the need to install plugins or download native apps. So, the vulnerability is in the Chromium Open Source Software (OSS) which is consumed by Microsoft Edge. Google is aware that an exploit for this vulnerability exists in the wild. If you’re using Microsoft Edge (Chromium-based), make sure it gets updated as soon as possible.

Azure Site Recovery RCEs and EOPs

There are also a lot of vulnerabilities in Azure Site Recovery in July Patch Tuesday. Both EoPs and RCEs, and quite a few with non-public exploits of the POC maturity level. According to the description “Site Recovery is a native disaster recovery as a service (DRaaS)”, it would seem that this should be patched by Microsoft themselves. But in fact, there is a Microsoft Azure Site Recovery suite installed on the hosts, and at least some of the vulnerabilities were found in it.

Let’s see, for example, Elevation of Privilege in Azure Site Recovery (CVE-2022-33675). The vulnerability was discovered and reported to Microsoft by Tenable researcher Jimi Sebree. The Microsoft Azure Site Recovery suite contains a DLL hijacking flaw that allows for privilege escalation from any low privileged user to SYSTEM. 

Incorrect permissions on the service’s executable directory (E:\Program Files (x86)\Microsoft Azure Site Recovery\home\svsystems\transport\) allow new files to be created by any user. The service launched from this directory runs automatically and with SYSTEM privileges and attempts to load several DLLs from this directory. This allows for a DLL hijacking/planting attack via several libraries that are attempted to be loaded from this location when the service is launched. Existing deployments should ensure that the Microsoft-supplied patches have been appropriately applied.

The full Vulristics report is available here: ms_patch_tuesday_july2022_report

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