Windows Secure Kernel Mode Elevation of Privilege Vulnerability

Security Vulnerability

Released: Aug 7, 2024

Last updated: Aug 13, 2024

Assigning CNA
Microsoft
CVE.org link
CVE-2024-21302
Impact
Elevation of Privilege
Max Severity
Important
Weakness
CVSS Source
Microsoft
Vector String
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

Please see Common Vulnerability Scoring System for more information on the definition of these metrics.

Executive Summary

Summary:

Microsoft was notified that an elevation of privilege vulnerability exists in Windows based systems supporting Virtualization Based Security (VBS), including a subset of Azure Virtual Machine SKUS. This vulnerability enables an attacker with administrator privileges to replace current versions of Windows system files with outdated versions. By exploiting this vulnerability, an attacker could reintroduce previously mitigated vulnerabilities, circumvent some features of VBS, and exfiltrate data protected by VBS.

Microsoft is developing a security update to mitigate this threat, but it is not yet available. Guidance to help customers reduce the risks associated with this vulnerability and to protect their systems until the mitigation is available in a Windows security update is provided in the Recommended Actions section of this CVE.

This CVE will be updated when the mitigation is available in a Windows security update. We highly encourage customers to subscribe to Security Update Guide notifications to receive an alert when this update occurs.

Update: August 13, 2024

Microsoft has released the August 2024 security updates that include an opt-in revocation policy mitigation to address this vulnerability. Customers running affected versions of Windows are encouraged to review KB5042562: Guidance for blocking rollback of virtualization-based security related updates to assess if this opt-in policy meets the needs of their environment before implementing this mitigation. There are risks associated with this mitigation that should be understood prior to applying it to your systems. Detailed information about these risks is also available in KB5042562.

Details:

A security researcher informed Microsoft of an elevation of privilege vulnerability in Windows 10, Windows 11, Windows Server 2016, and higher based systems including Azure Virtual Machines (VM) that support VBS. For more information on Windows versions and VM SKUs supporting VBS, reference: Virtualization-based Security (VBS) | Microsoft Learn.

The vulnerability enables an attacker with administrator privileges on the target system to replace current Windows system files with outdated versions. Successful exploitation provides an attacker with the ability to reintroduce previously mitigated vulnerabilities, circumvent VBS security features, and exfiltrate data protected by VBS.

Microsoft is developing a security update that will revoke outdated, unpatched VBS system files to mitigate this vulnerability, but it is not yet available. Due to the complexity of blocking such a large quantity of files, rigorous testing is required to avoid integration failures or regressions. This CVE will be updated with new information and links to the security updates once available. We highly encourage customers subscribe to Security Update Guide notifications to be alerted of updates. For more information see Microsoft Technical Security Notifications and Security Update Guide Notification System News: Create your profile now – Microsoft Security Response Center

Microsoft is not aware of any attempts to exploit this vulnerability. However, a public presentation regarding this vulnerability was hosted at BlackHat on August 7, 2024. The presentation was appropriately coordinated with Microsoft but may change the threat landscape. Customers concerned with these risks should reference the guidance provided in the Recommended Actions section to protect their systems.

Microsoft has released an opt-in mitigation available as an interim solution to help protect customers concerned about this vulnerability until the final mitigation is available in a security update.

Caution: There are risks associated with this mitigation that should be understood prior to applying it to your systems. Detailed information about these risks is also available in KB5042562.The following recommendations do not mitigate the vulnerability but can be used to reduce the risk of exploitation until the security update is available.

Detections:

A detection has been added to Microsoft Defender for Endpoint (MDE) to alert customers using this product of an exploit attempt. Instructions for how Azure customers can integrate and enable MDE with Defender for Cloud are found here:

Note: False positives may be triggered by legitimate operations due to detection logic. Customers should investigate any alert for this detection to validate the root cause.

Exploitability

The following table provides an exploitability assessment for this vulnerability at the time of original publication.

Publicly disclosed
Yes
Exploited
No
Exploitability assessment
Exploitation Less Likely

FAQ

What privileges could be gained by an attacker who successfully exploited this vulnerability?

An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.

Acknowledgements

  • Alon Leviev with SafeBreach
Microsoft recognizes the efforts of those in the security community who help us protect customers through coordinated vulnerability disclosure. See Acknowledgements for more information.

Security Updates

To determine the support lifecycle for your software, see the Microsoft Support Lifecycle.

Release date Descending

Disclaimer

The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

Revisions

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