CVE-2022-33679: 
vulnerability analysis and mitigation

CVE-2022-33679 is a Windows Kerberos Elevation of Privilege vulnerability disclosed on September 13, 2022. The vulnerability was discovered by James Forshaw of Google Project Zero and affects Windows domain accounts that have pre-authentication disabled. This vulnerability enables an attacker to perform an encryption downgrade attack targeting the Kerberos authentication protocol in Windows environments (Horizon3 Blog).

The vulnerability exploits a weakness in the Kerberos authentication process by forcing the Key Distribution Center (KDC) to use the RC4-MD4 encryption algorithm. The attack performs an encryption downgrade attack by manipulating the AS-REQ (Authentication Service Request) to force the use of RC4-MD4, followed by a brute force attack on the session key using known plaintext. When successful, the attacker obtains both a Ticket-Granting-Ticket (TGT) and a session key, which can be used to request service tickets. The vulnerability has been assigned a CVSS v3.1 base score of 8.1 (HIGH) with the vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H (NVD).

The successful exploitation of this vulnerability allows an unauthenticated attacker to perform Kerberoasting attacks without requiring valid domain credentials. This can lead to the compromise of service accounts through offline password cracking of service tickets, potentially enabling lateral movement and privilege escalation within the domain, as many services run with elevated privileges (Horizon3 Blog).

There are several mitigation strategies available: 1) Ensure pre-authentication is enabled for all accounts where possible, as it is disabled by default, 2) Disable the RC4-MD4 encryption algorithm through system configuration, though this may impact compatibility with some legacy systems, 3) Enforce Kerberos Armoring (FAST) on all clients and KDCs in the environment. Regular audits should be conducted to identify accounts with pre-authentication disabled (Horizon3 Blog).