Lenovo warns of flaws that can be used to bypass security features

Lenovo fixed two high-severity flaws impacting various laptop models that could allow an attacker to deactivate UEFI Secure Boot.

Lenovo has released security updates to address a couple of high-severity vulnerabilities impacting various ThinkBook, IdeaPad, and Yoga laptop models. An attacker can exploit the flaws to disable UEFI Secure Boot.

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 root cause of the flaws is the use of a vulnerable driver during the manufacturing process for some Lenovo devices that was mistakenly not deactivated.

Below are the vulnerabilities that were reported in Lenovo Notebook BIOS.

CVE-2022-3430: A potential vulnerability in the WMI Setup driver on some consumer Lenovo Notebook devices may allow an attacker with elevated privileges to modify secure boot setting by modifying an NVRAM variable.
CVE-2022-3431: A potential vulnerability in a driver used during manufacturing process on some consumer Lenovo Notebook devices that was mistakenly not deactivated may allow an attacker with elevated privileges to modify secure boot setting by modifying an NVRAM variable.
CVE-2022-3432: A potential vulnerability in a driver used during manufacturing process on the Ideapad Y700-14ISK that was mistakenly not deactivated may allow an attacker with elevated privileges to modify secure boot setting by modifying an NVRAM variable.

The vulnerabilities were reported to the vendor by Martin Smolár from ESET.

“While disabling UEFI Secure Boot allows direct execution of unsigned UEFI apps, restoring factory default dbx enables the use of known vulnerable bootloaders (e.g., #CVE-2022-34301 found by @eclypsium) to bypass Secure Boot, while keeping it enabled.” reads one of the tweets published by ESET.

The experts pointed out that an attacker can trigger the flaws by simply creating special NVRAM variables. The researcher Nikolaj Schlej recently posted a nice explanation of why and how firmware developers should avoid storing security-sensitive components in NVRAM variables:

Owners of the affected devices are highly recommended to update to the latest firmware version. Visiting Lenovo advisory it is possible to determine if a device is affected by these vulnerabilities and receive firmware update instructions.

The firmware versions that fix the vulnerabilities are mentioned under the CVE IDs, so make sure to upgrade to that version or later.

For official Lenovo software, check out this online support portal or run the update tool pre-installed on your computer.

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Pierluigi Paganini

(SecurityAffairs – hacking, Secure Boot)

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Pierluigi Paganini

Pierluigi Paganini is member of the ENISA (European Union Agency for Network and Information Security) Threat Landscape Stakeholder Group and Cyber G7 Group, he is also a Security Evangelist, Security Analyst and Freelance Writer. Editor-in-Chief at "Cyber Defense Magazine", Pierluigi is a cyber security expert with over 20 years experience in the field, he is Certified Ethical Hacker at EC Council in London. The passion for writing and a strong belief that security is founded on sharing and awareness led Pierluigi to find the security blog "Security Affairs" recently named a Top National Security Resource for US. Pierluigi is a member of the "The Hacker News" team and he is a writer for some major publications in the field such as Cyber War Zone, ICTTF, Infosec Island, Infosec Institute, The Hacker News Magazine and for many other Security magazines. Author of the Books "The Deep Dark Web" and “Digital Virtual Currency and Bitcoin”.