Researchers from the University of Birmingham, known for developing the Plundervolt and VoltPillager attacks, have identified a vulnerability (CVE-2022-43309) in certain server motherboards that allows for physical damage to the CPU with no possibility of recovery. The vulnerability, codenamed PMFault, can be exploited to harm servers that the attacker does not have physical access to but has privileged access to the operating system, obtained, for example, through the exploitation of an unpatched vulnerability or through admin credentials interception.
The essence of the proposed method lies in using the PMBus interface, which employs the I2C protocol, to increase the voltage supplied to the processor to levels that can damage the chip. The PMBus interface is typically implemented in the VRM (Voltage Regulator Module), which can be accessed through manipulation of the BMC controller. To execute an attack on PMBus-supported boards, in addition to having admin privileges in the operating system, it is necessary to have programmatic access to the BMC (Baseboard Management Controller), for example, through the IPMI KCS (Keyboard Controller Style) interface, via Ethernet, or through reprogramming the BMC from the current system.
The presence of a vulnerability that allows for an attack without knowledge of authentication parameters in the BMC has been confirmed in Supermicro motherboards with IPMI support (X11, X12, H11, and H12) and ASRock, but other server boards that allow access to PMBus are also affected. In experiments conducted, two Intel Xeon processors were damaged when the voltage was increased to 2.84 volts on these boards. To access the BMC without knowledge of authentication parameters while having root access to the operating system, a vulnerability in the firmware verification mechanism was used, allowing the loading of a modified firmware update into the BMC controller, as well as the ability for unauthenticated access via IPMI KCS.
The method of voltage alteration via PMBus can also be used to execute a Plundervolt attack, allowing damage to the contents of data cells in the CPU by reducing the voltage to minimal levels, affecting computations in Intel SGX isolated enclaves and generating errors in originally correct algorithms. For instance, changing the value used during multiplication in the encryption process can result in incorrect ciphertext. If an attacker can access the handler in SGX for encrypting their data, they can cause failures to gather statistics about the changes in the output ciphertext and recover the key value stored in the SGX enclave.
The toolkit for executing attacks on Supermicro and ASRock motherboards, as well as a utility to check for access to PMBus, has been published on GitHub.
Source: opennet.ru
