CVE-2023-29343: SysInternals Sysmon for Windows Elevation of Privilege Vulnerability

Attention Windows administrators and users! A newly discovered vulnerability (CVE-2023-29343) within Sysinternals Sysmon for Windows may allow for an elevation of privilege attack. This high severity vulnerability should not be ignored; read on for information on the details of the vulnerability, how it can be exploited, and steps to mitigate the issue.

Background

Sysinternals Sysmon (or System Monitor) is a Windows system service and device driver that monitors and logs various system operations. It is a valuable tool for administrators in tracking and auditing various activities on their systems. However, this previously undiscovered vulnerability leaves systems vulnerable to potential attacks.

Microsoft has provided a detailed summary of the vulnerability and assigned it a CVE ID (CVE-2023-29343) for tracking and documentation purposes. You can monitor the CVE details at the following link:

CVE-2023-29343

Vulnerability Details

The vulnerability lies in the elevation of privilege during the handling of certain syscalls by Sysmon. An attacker with local access to a system can abuse this vulnerability to gain SYSTEM-level access, enabling them to execute arbitrary code, install programs, or view and modify user data. The malicious code could be executed in the context of the SYSTEM account, which has unrestricted privileges.

Here is a snippet of the code with the vulnerable section

NTSTATUS vulnerable_syscall_handler(...)
{
    ...
    // Sysmon look for vulnerable syscall
    if (search_vulnerable_syscall(pid)) {
        // Elevation of privilege flaw
        status = elevate_privilege();
        ...
    }
    return status;
}

By exploiting this vulnerability, an attacker would be able to execute the elevate_privilege() function and elevate their privilege without proper authorization. This successful exploit results in gaining unauthorized access to the entire system, breaking the barrier of security measures in place.

Exploit Details

An attacker must have local access to the target system to exploit this vulnerability. Leveraging this access, the attacker can craft a specifically tailored program that hooks into the Sysmon vulnerable syscall handler. The crafted program gains SYSTEM access, enabling the attacker to take full control of the target system, all while remaining undetected by the installed security measures.

To protect your systems from exploitation, implement the following steps

1. Verify your Sysmon version: Review your Sysmon installation and ensure you are running the latest version of the software. Vulnerable versions prior to 13.x should be promptly upgraded.
2. Apply patches: As soon as Microsoft provides a security update, apply the patch to your systems. Security updates address the vulnerability in the up-to-date, maintained releases of Sysmon. Subscribe to Microsoft Security Response Center for the latest updates.
3. Limit local access: Restrict the number of users and applications with local access to your systems. Following the principle of least privilege minimizes the attack surface and reduces the risk of exploitation.
4. Monitor logs: Regularly review the logs generated by Sysmon. These logs can help you identify anomalies and unauthorized access attempts and potentially lead to earlier detection of an intrusion or exploitation.

Although no known exploits are circulating in the wild, it is crucial to act promptly and defend your systems from this elevation of privilege vulnerability. By adhering to these mitigation steps, you're ensuring the continued security of your organization's Windows systems and minimizing the chance of unauthorized access to critical data and resources.

Timeline

Published on: 05/09/2023 18:15:00 UTC
Last modified on: 05/16/2023 14:57:00 UTC