CVE-2022-35276 - Privilege Escalation via Improper Access Control in Intel NUC 8 Compute Elements BIOS

In the world of system security, BIOS vulnerabilities don't appear as frequently as software bugs, but when they do, the risk is serious. CVE-2022-35276 is one such vulnerability that threatens certain Intel NUC 8 Compute Elements BIOS versions before CBWHL357.0096. Let’s break down what happened, how attackers can exploit this bug, and what you should do about it.

What is CVE-2022-35276?

CVE-2022-35276 is an improper access control vulnerability found in the BIOS firmware of some Intel(R) NUC 8 Compute Elements. By exploiting this, a local user with privileges could potentially escalate those privileges even further, gaining more control than intended.

Affected products:

Intel rates this as a medium-severity vulnerability.

Official Intel advisory:
- INTEL-SA-00739

How Does the Vulnerability Work?

The vulnerability stems from improper access controls in the BIOS. While BIOS is usually well-protected, mistakes or oversights in permissions can let users tweak or bypass security features. Specifically, on older BIOS versions, certain critical operations weren’t properly locked down after boot, so a user with enough local access (like an administrator or someone with physical access) could potentially:

Disable security features, opening the way for further compromise

This is mostly a local privilege escalation scenario, meaning the attacker already needs access to the system.

The Exploit: How Can Attackers Take Advantage?

To keep things clear and non-malicious, I’ll outline a basic exploitation scenario.

1. Attacker gains local admin

The attacker needs local OS-level privileges. This could be someone with physical access, a malicious insider, or someone who has already breached the OS.

Intel's Flash Programming Tool (FPT) - often found in Intel’s ME System Tools suite

- Third-party tools capable of reading/writing BIOS regions if unchecked

Because of improper access control, the attacker might be able to run commands like

REM Dump BIOS region to confirm read/write access
fptw64.exe -d dump.bin

REM Try to flash a malicious/fake BIOS
fptw64.exe -f malicious_bios.bin

Normally, BIOS region access is locked post-boot via the FLOCKDN bit (Flash Lock Down). When that fails (as in this CVE), the lock isn't properly enforced.

A sample pseudo-code scenario

// Check if firmware region is locked
if(!is_bios_flash_locked()) {
    // write new settings or disable protections
    write_malicious_settings();
}

An attacker could upload a tampered BIOS with a backdoor or disable UEFI Secure Boot, making the system vulnerable to rootkits.

Why This Matters

Most organizations trust the BIOS layer—if that’s compromised, no software running on the device can be fully trusted. Exploiting this vulnerability, attackers could:

Proof-of-Concept Example

_Disclaimer:_ This example is for educational purposes. Do not use this information for unauthorized access.

Assume an attacker has acquired admin on Windows 10 running an old BIOS version

# Use Intel's FPT tool to check lock status
Start-Process -Verb runAs ".\fptw64.exe" -ArgumentList "-i"

# If the lock is off, dump BIOS, modify, and reflash it
Start-Process -Verb runAs ".\fptw64.exe" -ArgumentList "-d dump.bin"
Start-Process -Verb runAs ".\fptw64.exe" -ArgumentList "-f modified.bin"

If lock protections are missing, these commands succeed, letting the attacker upload custom firmware.

Intel BIOS Updates:

NUC 8 Compute Element downloads

Only let trusted users have admin or local access.

- Enable physical/tamper protections in BIOS settings.

Summary Table

| Impacted Model | Vulnerable BIOS | Severity | Fix Available | Exploit Requires |
|---------------------|-----------------|----------|---------------|--------------------|
| NUC 8 Compute Element | CBWHL357.0095 or earlier | Medium | Yes (0096+) | Local privileged access |

Final note: BIOS security is backbone security—always patch early, and lock down who can touch your firmware!

Timeline

Published on: 11/11/2022 16:15:00 UTC
Last modified on: 11/16/2022 18:56:00 UTC