OpenBSD discontinues support for Intel CPU Hyper-Threading

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Ngày cập nhật gần nhất: 15/4/2026

Due to security concerns related to the threat named 'Spectre vulnerability', OpenBSD project will discontinue support for Intel CPU Hyper-Threading

Hyper-Threading (HT) is an Intel proprietary technology that allows processors to execute parallel activities on different cores within the same multi-core CPU.

This technology has been integrated into all Intel CPUs released since 2002 and is enabled by default to enhance device performance.

OpenBSD discontinues support for Intel CPU Hyper-Threading

Intel HT vulnerable to timing attack

Today, Mark Kettenis of the OpenBSD project announced that the OpenBSD development team has removed support for Intel Hyper-Threading (HT). The reason is because the design of this technology opens the door to timing attacks.

Timing attacks are part of cryptographic attacks, through which a third-party observer can deduce the content of encrypted data by recording and analyzing the execution time of encryption algorithms.

Recent disclosures of Meltdown and Spectre vulnerabilities along with their variants have all been timing attack exploits at the CPU core level.

According to Kettenis, Intel HT could make timing attacks easier, opening up opportunities for attackers to exploit spectre-class vulnerabilities.

New Sysctl available for certain OpenBSD versions

The OpenBSD development team has added new settings to disable HT support, as most new devices no longer provide the ability to disable hyper-threading in the BIOS setup, refer to how to access BIOS here.

Frequently Asked Questions

What is the reason for OpenBSD discontinuing Intel Hyper-Threading support?

OpenBSD has discontinued support for Intel Hyper-Threading due to security concerns related to timing attacks, which can exploit vulnerabilities like Meltdown and Spectre. This design flaw allows attackers to analyze the execution time of encryption algorithms, potentially compromising encrypted data.

How does Intel Hyper-Threading affect CPU performance and security?

Intel Hyper-Threading is designed to enhance CPU performance by enabling parallel processing across multiple cores. However, this technology has been shown to increase the risk of timing attacks, which can compromise security by allowing unauthorized access to encrypted information.

What new settings has OpenBSD implemented regarding Hyper-Threading?

OpenBSD has introduced new Sysctl settings to disable Hyper-Threading support. This adjustment is necessary as many modern devices lack the BIOS option to disable HT, enhancing security by mitigating potential timing attack vulnerabilities.

What are timing attacks and how are they related to Intel Hyper-Threading?

Timing attacks are a form of cryptographic attack that exploits the time taken to execute encryption algorithms. Intel Hyper-Threading can exacerbate this vulnerability by allowing attackers to glean information from the timing of operations on the CPU, thus endangering encrypted data.

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