Microsoft’s April 2022 Patch Tuesday Addresses 117 CVEs (CVE-2022-24521)

CVE-2022-24521 is an EoP vulnerability in the Windows Common Log File System (CLFS) driver for Microsoft Windows. EoP flaws like this one are leveraged post-authentication, after an attacker has successfully accessed a vulnerable system, to gain higher permissions. According to Microsoft, this flaw has been exploited in the wild as a zero-day, though we do not have any additional details about its exploitation. We do know that it was reported to Microsoft by the National Security Agency along with researchers at CrowdStrike. Organizations should ensure they apply the available patches as soon as possible. CVE-2022-24481 is another EoP in the CLFS driver that received the same CVSSv3 score of 7.8 and was rated “Exploitation More Likely” according to Microsoft’s Exploitability Index. However, it is not a zero-day.

CVE-2022-26904 is an EoP vulnerability in the Windows User Profile service. It received a CVSSv3 score of 7.0, which rates its severity as important. The attack complexity for this flaw is considered high because it “requires an attacker to win a race condition.” Despite the higher complexity, it is still considered as “Exploitation More Likely.” This is the second of two zero-days addressed this month, as details about this vulnerability were publicly disclosed prior to a patch being made available.

CVE-2022-24491 is a critical RCE vulnerability in the Windows Network File System (NFS) that received a CVSSv3 score of 9.8 and a rating of “Exploitation More Likely.” An unauthenticated, remote attacker could exploit this vulnerability by sending specially crafted NFS protocol network messages to a vulnerable system. Only systems with the NFS role enabled are at risk for exploitation; however, organizations should still apply the patch to all systems to ensure they are protected.

CVE-2022-26809 is a critical RCE vulnerability in the Remote Procedure Call (RPC) runtime. It received a CVSSv3 score of 9.8. An unauthenticated, remote attacker could exploit this vulnerability by sending “a specially crafted RPC call to an RPC host.” Patching is the best approach to fully address this vulnerability; however, if patching is not feasible, Microsoft recommends blocking TCP port 445 on the perimeter firewall to mitigate attempts to exploit this flaw. Despite applying this mitigation, systems could “still be vulnerable to attacks from within their enterprise perimeter.”

CVE-2022-26817 and CVE-2022-26814 are RCE vulnerabilities in Windows DNS Server affecting Active Directory Domain Services that both received a CVSSv3 score of 6.6 and were discovered by Yuki Chen with Cyber KunLun. Exploitation of this vulnerability is rated “Less Likely” which may be tied to the higher attack complexity and required permissions. To successfully exploit this flaw, an attacker on the target network with permissions to query the domain name service must win a race condition. Only if they perfectly time exploitation of this vulnerability, can they achieve RCE. Patches have been released for supported versions for Windows Server and Windows Server Core installations.

This month, Microsoft patched 15 EoP vulnerabilities in Print Spooler components all of which received CVSSv3 scores of 7.8. Three of the vulnerabilities were disclosed by George Hughey of Microsoft Security Response Center Vulnerabilities and Mitigations and the other 12 were disclosed by Microsoft Offensive Research and Security Engineering. While Microsoft rates these vulnerabilities as “Exploitation Less Likely,” attackers have exploited EoP flaws in Print Spooler in the past.