CVE-2023-23376: Windows Common Log File System Driver Elevation of Privilege Vulnerability - Detailed Analysis and Exploit Information

CVE-2023-23376 is a critical elevation of privilege vulnerability in the Windows Common Log File System (CLFS) driver. In this detailed analysis, we will take a comprehensive look at this vulnerability, cover the code snippet involved, provide links to original references, and discuss exploit information. By understanding the intricate details of this vulnerability, system administrators and security professionals can better protect their systems against potential attacks.

Vulnerability Overview

The Common Log File System (CLFS) driver is a Windows kernel-mode component responsible for managing and processing various log records. A vulnerability exists in the way the CLFS driver processes user-mode input data, leading to an elevation of privilege (EoP) scenario. This occurs because the driver improperly validates memory addresses and user-mode input data, allowing a malicious user-mode application to execute arbitrary code with kernel-level privileges.

An attacker who successfully exploits this vulnerability can gain full control over the affected system, allowing them to install malicious software, modify system settings, and create or delete user accounts, among other undesirable activities.

Code Snippet

The vulnerability lies within the following function in the clfs.sys driver.`

NTSTATUS
ClfsUserModeDataOperation(
    _In_ PCLFS_USERMODE_DATA Data,
    _In_ ULONG InputBufferLength
)
{
    NTSTATUS status;
    PVOID userBuffer;

    userBuffer = ExAllocatePoolWithTag(NonPagedPool, InputBufferLength, 'sflC');
    if (!userBuffer)
    {
        return STATUS_INSUFFICIENT_RESOURCES;
    }

    status = ProbeForRead(Data->pData, InputBufferLength);
    if (!NT_SUCCESS(status))
    {
        ExFreePoolWithTag(userBuffer, 'sflC');
        return status;
    }

    RtlCopyMemory(userBuffer, Data->pData, InputBufferLength);

    // ... Perform CLFS operations using manipulated user input ...

    ExFreePoolWithTag(userBuffer, 'sflC');
    return STATUS_SUCCESS;
}

The above function allocates kernel memory for the user-mode input data and then proceeds to probe and copy the data without proper validation of memory addresses or input data. This opens up a possibility for an attacker to manipulate the data in user mode and overflow the kernel memory buffer, ultimately leading to code execution at the kernel level.

Original References

- Microsoft's official advisory on this vulnerability can be found at CVE-2023-23376 | Windows Common Log File System Driver Elevation of Privilege Vulnerability.

- Further technical details on this vulnerability are available from SpecterOps Blog, where researchers provide a deep dive into the exploitation process and challenges they faced when developing a proof-of-concept.

To exploit this vulnerability, an attacker would need to perform the following steps

1. Create a user-mode application that allocates a memory buffer used as input for the ClfsUserModeDataOperation() function.

2. Craft malicious data and fill the allocated buffer with it. The malicious data must be carefully chosen to trigger the vulnerability and overwrite kernel memory, eventually leading to arbitrary code execution.

3. Trigger the vulnerability by invoking the ClfsUserModeDataOperation() function with the malicious data as an input.

4. If successful, the attacker will have full control over the system at the kernel level, allowing them to perform various malicious activities.

Please note that an exploit for this vulnerability requires local access to the target system. Remote exploitation may be possible but would require chaining this vulnerability with other vulnerabilities, such as remote code execution or memory corruption bugs.

Conclusion

CVE-2023-23376 is a serious security vulnerability that affects the Windows CLFS driver, tantamount to an elevation of privilege attack. An attacker with local access to a system can execute arbitrary code with kernel-level privileges if this vulnerability is exploited. As a result, it is crucial for system administrators and security professionals to understand and address this vulnerability.

Microsoft has released security updates to address this vulnerability, and users and system administrators are strongly encouraged to apply the patches as soon as possible. Patching your system is the most effective way to protect it from being exploited by this dangerous vulnerability.

Timeline

Published on: 02/14/2023 20:15:00 UTC
Last modified on: 02/23/2023 19:38:00 UTC