Hackers remotely flip up the voltage on motherboards to brick servers

Presenting at Black Hat Asia 2023, an infosec researcher detailed how distant updates may be exploited to switch voltage on a Supermicro motherboard and remotely brick machines.

The College of Birmingham duo behind the invention prefer to mess around with voltage. They’re accountable for already revealing a vulnerability in Intel’s core microprocessor Software program Guard Extensions (SGX), generally known as Plundervolt, and a $30 2020 Intel SGX cloud server hack referred to as Voltpillager.

When the voltage of those techniques is altered, the encryption turns into weak and the hackers can extract delicate information.

Voltpillager was not a distant assault and required bodily proximity, corresponding to a rogue worker, so was restricted in risk scope. Plundervolt, whereas probably distant, required privileged entry to the working system and BIOS.

Intel issued firmware updates to forestall Plundervolt, however said that methods that require an attacker to bodily open a case, corresponding to Voltpillager, weren’t thought-about vulnerabilities.

The brand new energy administration fault, or PMFault, may be carried out by a privileged software program adversary who does not have entry to Board Administration Controller (BMC) login credentials. It permits the identical information extraction as its predecessor assaults, however by the BMC flash reminiscence chip.

The 2 researchers, Zitai Chen and David Oswald, mentioned in a January tutorial publication that “undervolting by the PMBus permits breaking the integrity ensures of SGX enclaves, bypassing Intel’s countermeasures in opposition to earlier undervolting assaults like Plundervolt.”

By then overvolting – sending 2.84 volts to the 1.52 spec’d CPU – the pair completely bricked two separate Xeon CPUs used within the experiment.

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They pinned the vulnerabilities on insecure firmware encryption and signing mechanisms, an absence of authentication in terms of firmware and IPMI KCS management interface upgrades, and the general motherboard design.

“I feel this assault is nicer than the VoltPillager,” mentioned Chen at Black Hat Asia 2023, including that it was “much less messy” as there have been fewer cables and no want to regulate temperature.

“With this assault we solely want the Ethernet cable to hook up with the server. And that is it. We needn’t open the field anymore.”

The duo’s massive takeaway is that trusted execution environments “like SGX should not solely depend on the safety of the CPU itself, but in addition of that of administration parts [in] the {hardware} design of the platform.”

Total, they advocate pondering of a server as an embedded system, declare that SGX attestation can’t measure BMC firmware, and warn that improper jumper configuration could cause safety points.

Chen and Oswald supply a PMBusDetect device for figuring out if a voltage regulator modeule is related to the PMBus. Nevertheless, they’ve solely but examined it on Reneseas ISL68137 and Monolithic MP2955.

Supermicro did reply to Chen and Oswald’s disclosure again in January. The {hardware} maker rated the vulnerability’s severity as “excessive” and issued new signed BMC firmware for all affected Supermicro motherboard SKUs.

That features those who incorporate the Clever Platform Administration Interface (IPMI) – the X11, X12, H11, and H12 product traces. ®