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Windows systems often depend on Kerberos for authentication, but security flaws in such foundational protocols can grant attackers unexpected power. In this deep dive, we’ll look at CVE-2022-30165—a significant Windows Kerberos Elevation of Privilege Vulnerability. We'll explain how it works, walk through technical details, see simplified code snippets, and discuss how it can be exploited if left unpatched.

What is CVE-2022-30165?

CVE-2022-30165 is a vulnerability that affects the way Kerberos, the main authentication protocol in Windows environments, processes privileges for users and services. More specifically, it allows attackers to gain SYSTEM-level privileges, which means an attacker could fully control a compromised Windows system.

User Interaction: None

Quick summary: If exploited, an attacker with a valid account can escalate their privileges from a limited user to local SYSTEM by abusing how Kerberos validates certain tickets.

How Does Kerberos Work? (Simplified)

Kerberos uses tickets to prove a user’s identity without sending passwords around the network. When you log in, you get a Ticket Granting Ticket (TGT). With the TGT, you can request more tickets to access specific services, like file shares or printing.

What’s the Problem With CVE-2022-30165?

The vulnerability lies in how the Kerberos Key Distribution Center (KDC) and the Local Security Authority Subsystem Service (LSASS) process ticket requests. Specifically, flawed validation lets attackers craft special (malicious) Kerberos tickets with elevated privileges.

In technical terms, a user who already has local access can manipulate attributes in a Kerberos ticket, tricking the KDC into granting higher privileges—such as SYSTEM. After this, the attacker gains full control of the device.

Initial Access: Attacker logs into a machine with valid but limited user credentials.

2. Crafting a Malicious Ticket: Attacker crafts and injects a manipulated Kerberos ticket that tricks the system about their identity and privileges.
3. Elevation: By sending the malicious ticket to the system, the attacker gets service tickets with SYSTEM privileges.
4. Full Control: Now the attacker can install programs, view/change/delete data, create accounts, and more.

Code Snippet: Abuse via Rubeus

Rubeus is a popular tool for Kerberos ticket operations. While Microsoft has patched the vulnerability, here's how a proof-of-concept ticket elevation could look using Rubeus, before patching:

# First, request a TGT for the compromised user
Rubeus.exe asktgt /user:victim /password:UserPassword

# Next, forge a ticket with extra privileges (note: only possible on an unpatched system/hardened domain controller)
Rubeus.exe tgtdeleg /ticket:hash /ptt

# Now, request admin tickets using the forged TGT
Rubeus.exe s4u /impersonateuser:Administrator /user:victim /rc4:hash /domain:DOMAIN.LOCAL /sid:S-1-5-21-... /ptt

# You may now have SYSTEM-level tickets loaded and can interact as SYSTEM

DISCLAIMER: For illustrative and educational purposes only. Never use attack tools on networks you do not own or have explicit permission to test.

Proof-of-Concept Demonstration

Security researcher Kevin Robertson (@kevin_robertson) has provided useful info on Kerberos attacks in general, though each CVE is unique. For CVE-2022-30165, in the wrong hands an attacker could easily automate the escalation with scripting tools already available in the public domain.

Patch your domain controllers and endpoints.

- Apply MS security update: Microsoft Security Update Guide - CVE-2022-30165
- Restrict permissions: Limit local admin rights and monitor ticket-granting requests in your environment.

References & Further Reading

- Microsoft CVE-2022-30165 Security Update Guide
- CVE Details
- Kerberos Authentication Overview
- Rubeus GitHub

Final Thoughts

Kerberos vulnerabilities like CVE-2022-30165 remind us how critical it is to keep up with patches. Even small flaws in authentication can hand attackers the power to take over entire networks. Protect yourself by patching quickly, reducing unnecessary privileges, and watching for suspicious activity, especially involving authentication systems.

Timeline

Published on: 06/15/2022 22:15:00 UTC
Last modified on: 07/06/2022 19:15:00 UTC