If you own or manage Intel NUC devices, particularly some models under the Intel(R) NUC Boards, NUC 8 Boards, NUC 8 Rugged Boards, or NUC 8 Rugged Kits, it’s time to check your firmware version. A vulnerability known as CVE-2022-26124 was found that could let a local, privileged attacker gain even more power, possibly to SYSTEM level, because of improper buffer restrictions in the BIOS. Below, we’ll break down what happened, how it works, and what you can do about it.

> Original Intel Security Advisory:
> INTEL-SA-00622

What Is CVE-2022-26124?

The vulnerability is an improper buffer restriction or buffer overflow in the BIOS firmware for some Intel NUC products.

Any version before CHAPLCEL.0059

Due to poor bounds-checking in the BIOS, a local attacker (already privileged, like an admin or root user) can trigger a buffer overflow that lets them run arbitrary code or change system operations. This could ultimately escalate their privileges even further or persist in ways that are tough to detect or remediate.

Technical Details: What’s Going On?

At its core, CVE-2022-26124 is all about buffer overflows — letting more data go into a buffer than it can safely hold, which then overwrites memory, typically letting an attacker control the code flow.

Where Is the Flaw?

The flaw is in the BIOS code — specifically, in how some functions handle data provided by high-privileged local users (for example, through system management interrupts (SMIs) or UEFI variable updates).

Here’s a simple, high-level (pseudo-code) illustration of what the vulnerable code might look like

void vulnerable_bios_function(char *input) {
    char buffer[128];
    strcpy(buffer, input); // No check on input length!
    // ...do something with buffer...
}

If an attacker sends more than 128 bytes through input, the extra bytes “spill” past the end of buffer, potentially overwriting instructions or sensitive pointers in the BIOS's memory space.

Bypassing OS Protections:

Since this is BIOS-level, OS security features (like Windows UAC or Linux permissions) aren’t enough to stop this.

Exploit Example: How It Might Look

Here’s a simplified, educational example (DO NOT RUN ON PRODUCTION) showing what an exploit might look like in a classic buffer overflow:

import os

# Let's pretend the NUC firmware exposes a vulnerable SMI handler via /dev/smm_device
# and the 'write_bios_config' function passes input directly to that handler.

overflow_payload = b"A" * 200  # 200 bytes is over the 128-bytes limit

# This just simulates opening a BIOS handler as a device file for writing
with open("/dev/smm_device", "wb") as device:
    device.write(overflow_payload)

# The overflow could overwrite control structures, jumping to attacker code

> Note: Real exploitation is much more complex and would likely use reverse engineering tools (like UEFITool or Chipsec) to target the platform’s firmware chip.

Attackers can run code with firmware or SYSTEM-level privileges.

- Rootkits / Persistent Malware:
Because the firmware runs before the OS, malware can re-infect installed operating systems or hide from AV software.

Update Your BIOS

Head to Intel’s official support site and download at least CHAPLCEL.0059 or later for your device:
- Intel NUC BIOS Updates

Limit Local Privileged Users

Restrict who can get root/administrator access. Don’t give regular users local admin.

Monitor for Changes in Firmware

Use monitoring tools (like Intel Platform Firmware Resilience) to check for unauthorized firmware changes.

Intel Security Advisory (CVE-2022-26124):

https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00622.html

NIST NVD Entry:

https://nvd.nist.gov/vuln/detail/CVE-2022-26124

General Guide: BIOS Security:

Intel BIOS and UEFI Security

CHIPSEC for Firmware Testing:

https://github.com/chipsec/chipsec

Conclusion

CVE-2022-26124 is a reminder that not all security reside within the operating system. Firmware vulnerabilities are especially dangerous because they can be hard to detect, hard to clean, and may survive OS reinstallation. If you manage any Intel NUC machines, make sure you update your firmware right away and review who has high-level access!

Timeline

Published on: 11/11/2022 16:15:00 UTC
Last modified on: 11/17/2022 15:30:00 UTC