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MicrosoftKB5039885

HistoryJul 09, 2024 - 7:00 a.m.

July 9, 2024-KB5039885 Cumulative Update for .NET Framework 4.8 for Windows 10, version 1607 and Windows Server 2016

2024-07-0907:00:00

Microsoft

support.microsoft.com

151

windows 10

.net framework

security update

elevation of privilege

reliability improvements

cve-2024-38081

memory leaks

CVSS3

7.3

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

AI Score

7.8

Confidence

High

EPSS

0.001

Percentile

21.7%

JSON

July 9, 2024-KB5039885 Cumulative Update for .NET Framework 4.8 for Windows 10, version 1607 and Windows Server 2016

_ Revised August 28, 2024: _ Update breaking change details to known issue section._ Revised July 30, 2024: _ Add breaking change information to known issue section.

Release Date:
July 9, 2024 Version: ** .NET Framework 4.8**

The July 9, 2024 update for Windows 10, version 1607 and Windows Server 2016 includes security and cumulative reliability improvements in .NET Framework 4.8. We recommend that you apply this update as part of your regular maintenance routines. Before you install this update, see the Prerequisites and Restart requirement sections.

Summary

Security Improvements CVE-2024-38081 - .NET Framework Elevation of Privilege Vulnerability

This security update addresses a remote code execution vulnerability detailed in CVE-2024-38081.Quality and Reliability Improvements Winforms	- Addresses an issue with the size of memory leaks associated with AccessibleObjects held in memory due to ref-counting.

Known issues in this update

Breaking change details	The .NET Framework servicing update released on July 2024 security and quality rollup - .NET Framework contains a security fix addressed an elevation of privilege vulnerability detailed in CVE 2024-38081. The fix changed System.IO.Path.GetTempPath method return value. If windows version exposes the GetTempPath2 Win32 API, this method invokes that API and returns the resolved path. See the Remarks section of the GetTempPath2 documentation for more information on how this resolution is performed, including how to control the return value through the use of environment variables. The GetTempPath2 API may not be available on all versions of Windows. An observable difference between the GetTempPath and GetTempPath2 Win32 APIs is that they return different values for SYSTEM and non-SYSTEM processes. When calling this function from a process running as SYSTEM it will return the path %WINDIR%\SystemTemp, which is inaccessible to non-SYSTEM processes. This return value for SYSTEM processes cannot be overridden by environment variables. For non-SYSTEM processes, GetTempPath2 will behave the same as GetTempPath, respecting the same environment variables to override the return value.In some scenarios it may be possible to redirect the Temp folder to a different folder using environment variables or other means. Please refer to the official documentation for the GetTempPath2 Win32 API for the most up to date information on this behavior. Please reference to the System.IO.Path.GetTempPath API for more information.
Temporary workaround	⚠️Warning: The opt-out will disable the security fix for the elevation of privilege vulnerability detailed in CVE 2024-38081. The opt-out is only for temporary workaround if you’re sure that the software is running in secure environments. Microsoft does not recommend applying this temporary workaround.

Breaking change details

The .NET Framework servicing update released on July 2024 security and quality rollup - .NET Framework contains a security fix addressed an elevation of privilege vulnerability detailed in CVE 2024-38081. The fix changed System.IO.Path.GetTempPath method return value. If windows version exposes the GetTempPath2 Win32 API, this method invokes that API and returns the resolved path. See the Remarks section of the GetTempPath2 documentation for more information on how this resolution is performed, including how to control the return value through the use of environment variables. The GetTempPath2 API may not be available on all versions of Windows. An observable difference between the GetTempPath and GetTempPath2 Win32 APIs is that they return different values for SYSTEM and non-SYSTEM processes. When calling this function from a process running as SYSTEM it will return the path %WINDIR%\SystemTemp, which is inaccessible to non-SYSTEM processes. This return value for SYSTEM processes cannot be overridden by environment variables. For non-SYSTEM processes, GetTempPath2 will behave the same as GetTempPath, respecting the same environment variables to override the return value.In some scenarios it may be possible to redirect the Temp folder to a different folder using environment variables or other means. Please refer to the official documentation for the GetTempPath2 Win32 API for the most up to date information on this behavior. Please reference to the System.IO.Path.GetTempPath API for more information.

Temporary workaround

⚠️**Warning: **The opt-out will disable the security fix for the elevation of privilege vulnerability detailed in CVE 2024-38081. The opt-out is only for temporary workaround if you’re sure that the software is running in secure environments. Microsoft does not recommend applying this temporary workaround.

Option#1: Opt out in a command window by setting the environment variable
- COMPlus_Disable_GetTempPath2=true
Opiton#2: Opt out globally on the machine by creating a system-wide environment variable and rebooting to ensure all processes observe the change.
- System-wide environment variables can be set by running “sysdm.cpl” from a cmd window, and then navigating to “Advanced -> Environment variables -> System variables -> New”.
  Resolution| The API behavior change is by design to address the elevation of privilege vulnerability. Any affected software or application is expected to make code change to adapt to this new design change.

How to get this update

Install this updateRelease Channel	Available	Next Step
Windows Update and Microsoft Update	Yes	None. This update will be downloaded and installed automatically from Windows Update.
Windows Update for Business	Yes	None. This update will be downloaded and installed automatically from Windows Update.
Microsoft Update Catalog	Yes	To get the standalone package for this update, go to the Microsoft Update Catalog website.
Windows Server Update Services (WSUS)	Yes	This update will automatically sync with WSUS if you configure as follows: Product: Windows 10, version 1607 and Windows Server 2016Classification: Security Updates File information For a list of the files that are provided in this update, download the file information for cumulative update.

Prerequisites

To apply this update, you must have .NET Framework 4.8 installed.

Restart requirement

You must restart the computer after you apply this update if any affected files are being used. We recommend that you exit all .NET Framework-based applications before you apply this update.