Intel’s modem chips power fast 4G connectivity in laptops and mobile devices worldwide. However, security researchers discovered a significant vulnerability—CVE-2022-26079—in the Intel(R) XMM(TM) 756 Modem software, specifically prior to version M2_756_R_01.2146.00. In this post, we’ll break down what causes this bug, how an attacker can exploit it for privilege escalation, see some (sanitized) proof-of-concept code, and point you to references for further reading.

What is CVE-2022-26079?

CVE-2022-26079 is a vulnerability rooted in how the modem’s software checks conditions when performing certain operations. If you’re running a version older than M2_756_R_01.2146.00, and you have a privileged account on the system, you might be able to abuse bad logic checks in the Intel XMM 756 Modem driver to gain more power than you’re supposed to have.

Official Intel Description

> Improper conditions check in some Intel(R) XMM(TM) 756 Modem software before version M2_756_R_01.2146.00 may allow a privileged user to potentially enable escalation of privilege via local access. (source)

Where is the Vulnerability?

This bug lives in a Windows service or kernel-mode driver designed to talk to the modem hardware (common file names: XMM756.sys, or similar).

The “improper conditions check” means that the driver does not properly verify that an input or request is safe. For example, when handling a specific IOCTL (input/output control—a special way to ask Windows drivers to do things), the modem code might assume you've given good inputs, and skips thorough validation.

Suppose the driver exposes an IOCTL like IOCTL_XMM_PERFORM_OP, and expects specific input. If it only checks your access at a superficial level, or blindly trusts user-supplied data, you can trick it.

The Exploit: How Local Privilege Escalation Works

There is no public “turnkey” exploit for this CVE, but based on Intel’s description and past vulnerabilities with similar logic, here’s a plausible attack flow using straightforward logic.

Step 1: Gain Local Access

You need to be logged into the target system with some privilege—say as a regular admin or SYSTEM user.

Step 2: Craft Malicious IOCTL Input

Attackers will write a small Windows program that sends a cleverly malformed request to the driver, exploiting the condition check.

#### Sample: IOCTL Exploit Snippet (C/C++)

#include <windows.h>
#include <stdio.h>

#define IOCTL_XMM_VULN  x800E010  // Placeholder value; real values are specific to the driver

int main() {
    HANDLE hDevice = CreateFileA("\\\\.\\XMM756",
                                GENERIC_READ | GENERIC_WRITE,
                                ,
                                NULL,
                                OPEN_EXISTING,
                                FILE_ATTRIBUTE_NORMAL,
                                NULL);

    if (hDevice == INVALID_HANDLE_VALUE) {
        printf("Failed to open device: %lu\n", GetLastError());
        return 1;
    }

    DWORD bytesReturned;
    char inBuffer[64] = { /* malicious input data */ };
    char outBuffer[64] = {};

    if (!DeviceIoControl(
        hDevice, 
        IOCTL_XMM_VULN,
        inBuffer, sizeof(inBuffer),
        outBuffer, sizeof(outBuffer),
        &bytesReturned,
        NULL)) {
        printf("IOCTL failed: %lu\n", GetLastError());
    } else {
        printf("Driver responded. Potential vulnerability triggered!\n");
    }

    CloseHandle(hDevice);
    return ;
}


*This is illustrative; the real IOCTL code and data structures depend on reverse engineering the driver.*

Step 3: Abuse Logic for Privilege Escalation

Because the driver doesn’t check certain access conditions, your exploit can make it do things on your behalf (sometimes, writing kernel memory or escalating the process to SYSTEM).

Any system running the affected drivers before patch M2_756_R_01.2146.00

- Local attackers with admin or SYSTEM-level accounts (e.g., a malware that has already infected the computer)

Remediation

Upgrade Immediately  
Intel patched the bug in modem software version M2_756_R_01.2146.00 and newer. Reach out to your OEM (Dell, HP, Lenovo, etc.) for official driver updates if you're unsure.

- Intel Security Advisory INTEL-SA-00644 - CVE-2022-26079
- NIST NVD CVE-2022-26079 Entry
- Microsoft: DeviceIoControl *(for API reference)*

Final Notes

CVE-2022-26079 shows how even “privileged” software components from major vendors like Intel may include logic oversights that can give attackers dangerous power. If you’re a sysadmin or device security manager, check your modem/chipset driver versions promptly. And if you’re a developer working on hardware drivers, always validate ALL conditions—even if the operation looks safe on the surface.

Patching, strong user privilege separation, and constant security reviews help keep even the lowest-level code secure. Stay safe out there!

Timeline

Published on: 11/11/2022 16:15:00 UTC
Last modified on: 11/16/2022 18:16:00 UTC