CVE-2022-26923 - Active Directory Domain Services Elevation of Privilege Vulnerability

THE THREAT

Microsoft has disclosed a new vulnerability impacting Active Directory Certificate Services (ADCS) tracked as CVE-2022-26923 (Active Directory Domain Services Elevation of Privilege Vulnerability). If exploited successfully, an authenticated attacker can escalate privileges in environments where ADCS is running on the domain. eSentire is aware of technical details and tooling [2] for exploiting this vulnerability, increasing the risk this will be exploited in the wild. Impacted organizations are encouraged to prioritize testing and deployment of patches for CVE-2022-26923.

What we’re doing about it

• eSentire Managed Vulnerability Service has plugins in place to detect CVE-2022-26923
• eSentire’s Threat Response Unit is reviewing this topic for detection opportunities
• The Threat Response Unit provided details of known ADCS certificate misconfigurations in our May 2022 TRU Intelligence Brief. A recording can be found here [3]*.

*For eSentire customers, please reach out to your CSM for a non-gated version of the TRU Intelligence Brief recording from May 2022

What you should do about it

• Prioritize testing and patch deployment for CVE-2022-26923
• Consider reviewing ADCS certificates for known misconfigurations [4]

Additional information

On May 10th, 2022, Microsoft disclosed CVE-2022-26923 [1] (Active Directory Domain Services Elevation of Privilege Vulnerability). This vulnerability would allow a low-privileged user to escalate privileges to domain administrator when Active Directory Certificate Services is running on the domain.

Following Microsoft’s disclosure, the researcher who identified CVE-2022-26923 released technical details and updated tooling to exploit the vulnerability [2]. In essence, a low-privileged user could manipulate the dnsHostName property for their system and impersonate the machine name of a domain controller and request a certificate. This certificate can then be used for additional attacks, such as DCSync.

According to Microsoft “Before the May 10, 2022 security update, certificate-based authentication would not account for a dollar sign ($) at the end of a machine name. This allowed related certificates to be emulated (spoofed) in various ways.” [5]

We recommend reviewing Microsoft’s supplementary patch documentation on this issue for more information. We are also aware of post-patch issues [6] and recommend testing in your environment prior to patching.

References:

[1] https://msrc.microsoft.com/update-guide/vulnerability/CVE-2022-26923
[2] https://research.ifcr.dk/certifried-active-directory-domain-privilege-escalation-cve-2022-26923-9e098fe298f4
[3] https://www.brighttalk.com/webcast/15391/543073?utm_source=eSentire&utm_medium=brighttalk&utm_campaign=543073
[4] https://posts.specterops.io/certified-pre-owned-d95910965cd2
[5] https://support.microsoft.com/en-us/topic/kb5014754-certificate-based-authentication-changes-on-windows-domain-controllers-ad2c23b0-15d8-4340-a468-4d4f3b188f16
[6] https://www.reddit.com/r/sysadmin/comments/um9qur/patch_tuesday_megathread_20220510/i85p2ll/?context=3