Technical Advisory – NULL Pointer Derefence in McAfee Drive Encryption (CVE-2021-23893)

Vendor: McAfee
Vendor URL: https://kc.mcafee.com/corporate/index?page=content&id=sb10361
Versions affected: Prior to 7.3.0 HF1
Systems Affected: Windows OSs without NULL page protection 
Author: Balazs Bucsay <balazs.bucsay[ at ]nccgroup[.dot.]com> @xoreipeip
CVE Identifier: CVE-2021-23893
Risk: 8.8 - CWE-269: Improper Privilege Management

Summary

McAfee’s Complete Data Protection package contained the Drive Encryption (DE) software. This software was used to transparently encrypt the drive contents. The versions prior to 7.3.0 HF1 had a vulnerability in the kernel driver MfeEpePC.sys that could be exploited on certain Windows systems for privilege escalation or DoS.

Impact

Privilege Escalation vulnerability in a Windows system driver of McAfee Drive Encryption (DE) prior to 7.3.0 could allow a local non-admin user to gain elevated system privileges via exploiting an unutilized memory buffer.

Details

The Drive Encryption software’s kernel driver was loaded to the kernel at boot time and certain IOCTLs were available for low-privileged users.

One of the available IOCTL was referencing an event that was set to NULL before initialization. In case the IOCTL was called at the right time, the procedure used NULL as an event and referenced the non-existing structure on the NULL page.

If the user mapped the NULL page and created a fake structure there that mimicked a real Even structure, it was possible to manipulate certain regions of the memory and eventually execute code in the kernel.

Recommendation

Install or update Disk Encryption 7.3.0 HF1, which has this vulnerability fixed.

Vendor Communication

February 24, 2021: Vulnerability was reported to McAfee

March 9, 2021: McAfee was able to reproduce the crash with the originally provided DoS exploit

October 1, 2021: McAfee released the new version of DE, which fixes the issue

Acknowledgements

Thanks to the Cedric Halbronn for his support during the development of the exploit.

About NCC Group

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Published date:  October 4, 2021

Written by:  Balazs Bucsay