A flaw in some Acer laptops can be used to bypass security features

Pierluigi Paganini November 28, 2022

ESET announced the discovery of a vulnerability impacting Acer laptops that can allow an attacker to deactivate UEFI Secure Boot.

ESET researchers announced in a series of tweets the discovery of a vulnerability impacting Acer laptops, the issue can allow an attacker to deactivate UEFI Secure Boot.

The experts explained that the flaw, tracked as CVE-2022-4020, is similar to the Lenovo vulnerabilities the company disclosed earlier this month.

Same as in Lenovo’s case, an attacker can trigger the issue to deactivate the UEFI Secure Boot by creating NVRAM variable directly from OS.

The Secure Boot is a security feature of the latest Unified Extensible Firmware Interface (UEFI) 2.3.1 designed to detect tampering with boot loaders, key operating system files, and unauthorized option ROMs by validating their digital signatures. “Detections are blocked from running before they can attack or infect the system specification.”

An attacker that is able to bypass the Secure Boot could bypass any security measure running on the machine and achieve persistence even in case the OS is reinstalled.

The CVE-2022-4020 impacts certain versions of Acer Aspire A315-22 from Acer, the vulnerability resides in the HQSwSmiDxe DXE driver on these consumer Acer Notebook devices. Similar to the Lenovo issues an attacker with elevated privileges can exploit the bug to modify UEFI Secure Boot settings by modifying an NVRAM variable. The DXE driver BootOrderDxe simply disables UEFI Secure Boot if NVRAM variables “BootOrderSecureBootDisable” exists.

Acer UEFI bug

ESET explained that the flaws affects only 5 devices Aspire A315-22/22G, A115-21 and Extensa EX215-21/21G. According to Acer, an update should be distributed as a critical Windows update. Alternatively, the updated BIOS version can be downloaded here.

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Pierluigi Paganini

(SecurityAffairs – hacking, Moshen Dragon)

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