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*Published: June 2024*

The security landscape is always changing, with old vulnerabilities popping up in new places. In this exclusive deep-dive, we'll break down CVE-2022-26045, a critical flaw found in certain Intel® XMM™ 756 modem software that can lead to local privilege escalation if exploited. We'll examine what the bug is, how it can be exploited, and how to defend your devices. You'll also find sample code snippets and links to the official advisories.

What Is CVE-2022-26045?

CVE-2022-26045 is a software vulnerability found in some versions of the Intel XMM 756 modem—a widely used 4G/5G cellular modem solution. The flaw is rooted in improper buffer restrictions (also known as buffer overflow). This software bug existed in the modem's software before version M2_756_R_01.2146.00.

With physical access and elevated privileges, an attacker can leverage this bug to execute code at a higher privilege level than intended—essentially escalating their access and taking over sensitive parts of a device.

Buffer Overflows in Modem Firmware

Buffer overflow bugs happen when software lets too much data get written into memory, overflowing into neighboring memory locations. Attackers can use this to inject malicious code or corrupt important data structures, gaining unintended access.

Hypothetical Example

Let's say a function in the modem's firmware handled an input buffer for modem commands from a privileged user, but didn't check the buffer length:

// Example vulnerable code snippet

void process_modem_command(char *input) {
    char buffer[64];

    // Vulnerability: No bounds checking!
    strcpy(buffer, input);

    // ... process command ...
}

If the input string received is longer than 64 bytes, it could overwrite stack data—including the function's return address or security checks—leading to arbitrary code execution at higher privilege.

How Could an Attacker Exploit This?

Since this is a *local* bug (physical access needed), remote exploitation isn't possible. Here's a possible attack scenario:

Privileged Shell: The attacker logs in as a privileged user or roots the device.

3. Malicious Input: A custom binary or script feeds a specially crafted string through the modem's command interface, triggering the buffer overflow.
4. Privilege Escalation: Malicious code is injected, allowing the attacker to take over the modem software environment, which may give access to cellular data, communications, or extend to the OS itself in some platforms.

Sample Exploit (Hypothetical, for Research Only)

This is a simplified, illustrative Python snippet showing how a malicious payload might be sent. (Do *not* use this for malicious purposes!)

import serial

# Open serial port to modem
ser = serial.Serial('/dev/ttyUSB', baudrate=115200, timeout=1)

# Build malicious payload (80 bytes: 64 bytes to fill, 16 bytes to overflow)
payload = b'A' * 64 + b'B' * 16

# Send payload to modem
ser.write(payload)

# Close the port
ser.close()

Note: The real exploit may differ, as it depends on the specific firmware routines and hardware configuration.

Fixes & Mitigation

Intel has released a software update that patches this buffer overflow by improving length checking and restricting buffer usage.

Intel Security Advisory:

INTEL-SA-00698

CVE Detail:

CVE-2022-26045 at NVD

Firmware Update Info:

Intel XMM 756 Product Page

Summary

CVE-2022-26045 is an example of how even privileged paths within embedded software can expose major security risks. While this flaw can't be triggered remotely, it can make a big difference for attackers with physical access—like malicious insiders, repair techs, or those with stolen equipment.

Key advice: Always update device modems to the latest firmware, even if they're deep in the system. Physical access and local privilege don't mean "safe by default" in today's security climate.


*Stay tuned for more exclusive vulnerability breakdowns and practical security insights!*

Timeline

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