AMD last week said it was preparing patches for a vulnerability affecting the System Management Mode (SMM) of the Unified Extensible Firmware Interface (UEFI) shipped with systems that use certain notebook and embedded processors.
Discovered by security researcher Danny Odler in AMD’s Mini PC and tracked as CVE-2020-12890, the vulnerability is one of the three issues reported in April, allowing an attacker to manipulate secure firmware and execute arbitrary code while avoiding detection.
“AMD is aware of new research related to a potential vulnerability in AMD software technology supplied to motherboard manufacturers for use in their Unified Extensible Firmware Interface (UEFI) infrastructure and plans to complete delivery of updated versions designed to mitigate the issue by the end of June 2020,” the chip maker announced.
The company also explains that an attacker looking to exploit the vulnerability needs privileged physical or administrative access to a system that includes one of the affected AMD notebook or embedded processors.
“If this level of access is acquired, an attacker could potentially manipulate the AMD Generic Encapsulated Software Architecture (AGESA) to execute arbitrary code undetected by the operating system,” AMD says.
AMD, which has already delivered most of the updated versions of AGESA to its partners, says that only certain processors released between 2016 and 2019 are affected. The company advises users to ensure their devices are kept updated with the latest patches.
In a Medium post, Odler notes that “SMM is the most privileged code that can execute on x86 CPU,” and that it can be abused to target Kernel, Hypervisor, and other low level components as well.
The researcher identified three vulnerabilities in SMM, and says that all three of them feature a high severity rating. One of these issues (CVE-2020–14032) was fixed earlier this month, but the other two remain unpatched (one has yet to be issued a CVE identifier).