Privilege Escalation by user token - ties2/Red-Team GitHub Wiki

Privilege escalation is a significant issue in the cybersecurity domain. In the modern world, cybersecurity threats are becoming more advanced and diverse, and so is the threat of privilege escalation. A privilege escalation vulnerability is a security loophole that allows a user to access system resources and data that should only be accessible to an administrator. A user with privilege escalation vulnerability can gain higher access levels than they are allowed, which can cause significant harm to the system and its data.

One of the most common ways for attackers to gain escalated privileges is through user token vulnerability. In this essay, we will explore how user token vulnerabilities work, the risks they pose, and ways to prevent them. We will also examine real-world examples of user token vulnerability exploitation and its consequences.

Understanding User Token Vulnerability:

A user token is an object that identifies a user's security context. It contains various pieces of information such as user's group membership, privileges, and rights. A token is generated when a user logs into a system, and it is used to identify the user's security context when accessing system resources.

A user token vulnerability occurs when a user is granted excessive privileges or rights that allow them to perform actions beyond their authorization. These vulnerabilities can be the result of configuration errors, software bugs, or design flaws in the system.

When an attacker exploits a user token vulnerability, they gain escalated privileges, allowing them to access sensitive information or resources that they would otherwise be unable to access. This can be particularly dangerous in the case of systems that handle sensitive data, such as financial or healthcare systems.

Examples of User Token Vulnerability Exploitation:

One example of user token vulnerability exploitation is the infamous "Pass-the-Hash" attack. In this attack, an attacker gains access to a system with a low-privileged user account and then obtains the password hash of a privileged user. The attacker then uses the password hash to gain access to the privileged user's token, which allows them to access sensitive data and resources.

Another example of user token vulnerability exploitation is the "Token Kidnapping" attack. In this attack, an attacker gains access to a low-privileged user account and then exploits a vulnerability to hijack the token of a privileged user. The attacker can then use the hijacked token to perform actions that they are not authorized to perform, such as accessing sensitive data or creating new user accounts with escalated privileges.

User tokens can be vulnerable to exploitation in a number of ways. One common vulnerability is through the use of improperly configured service accounts. Service accounts are special user accounts that are used by Windows services to perform tasks on behalf of the system or other users. If a service account is configured with excessive privileges, an attacker who gains access to that account can potentially use it to escalate their own privileges.

Another way that user tokens can be exploited is through the use of Windows API functions that are vulnerable to manipulation. For example, the "CreateProcessWithTokenW" function can be used to start a new process with a specified user token. If an attacker can modify the parameters of this function to use a token with higher privileges than their own, they can use it to escalate their privileges and gain access to resources that they would not normally be able to access.

A more advanced method of exploiting user token vulnerabilities is through the use of "token kidnapping" attacks. In these attacks, an attacker gains access to a user's token and then uses it to create a new process with higher privileges. This can be done by modifying the memory of a running process to steal its token or by using a vulnerability in a system process to hijack a token. Once the attacker has a higher-privileged token, they can use it to escalate their privileges and gain access to sensitive resources on the system.

One example of a user token vulnerability is the "Windows Elevation of Privilege Vulnerability" (CVE-2020-0787). This vulnerability allowed attackers to exploit the Windows Task Scheduler to escalate their privileges on a system. By creating a scheduled task with a manipulated parameter, an attacker could trigger a bug in the task scheduler that would allow them to escalate their privileges to the level of the SYSTEM account.

Another example is the "Windows Impersonation Level Vulnerability" (CVE-2019-1315), which allowed attackers to escalate their privileges by exploiting a flaw in the Windows Remote Desktop Protocol (RDP) service. By sending a specially crafted packet to a vulnerable RDP server, an attacker could trick the server into giving them a higher-privileged token than their own, which they could then use to escalate their privileges and gain access to sensitive resources.

Preventing User Token Vulnerabilities:

Preventing user token vulnerabilities requires a multi-faceted approach that includes both technical and non-technical solutions. Some of the best practices to prevent user token vulnerabilities include:

  • Regularly patching and updating systems to address known vulnerabilities.

  • Implementing proper access controls to ensure that users only have the minimum level of access necessary to perform their job functions.

  • Restricting administrative privileges to only those users who require them to perform their job functions.

  • Implementing multi-factor authentication to reduce the risk of password-related attacks.

  • Implementing intrusion detection and prevention systems to detect and prevent attacks in real time.

Conclusion:

  • Privilege escalation attacks can be devastating for organizations, as they can provide attackers with unrestricted access to sensitive data and system resources. User token vulnerabilities are a common attack vector for privilege escalation, as they allow attackers to impersonate privileged users and execute commands with system-level privileges.

  • To prevent user token vulnerabilities, organizations should implement measures such as endpoint security solutions, the principle of least privilege, and security tools like EMET or Windows Defender Exploit Guard. By taking these steps, organizations can reduce the risk of privilege escalation attacks and protect their systems and data from unauthorized access and modification.

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