Recent research from ETH Zurich has uncovered new vulnerabilities affecting Intel and AMD CPUs on Linux, specifically targeting speculative execution attacks that can bypass existing Spectre mitigations. The vulnerabilities primarily impact Intel’s 12th, 13th, and 14th generation consumer processors, as well as the 5th and 6th generation Xeon chips. AMD’s older Zen 1, Zen 1+, and Zen 2 microarchitectures are also susceptible. The research highlights that these attacks undermine the Indirect Branch Predictor Barrier (IBPB), a critical defense mechanism designed to protect against speculative execution threats.
Speculative execution is a performance optimization feature in modern CPUs, allowing them to execute instructions before knowing if they will be needed. However, this mechanism can lead to side-channel risks, such as Spectre, where sensitive data might be accessed through CPU cache manipulation. The ETH Zurich researchers introduced two novel attacks: a cross-process attack on Intel and a PB-inception attack on AMD. These attacks enable hackers to hijack speculative return targets, leaking sensitive information despite the application of IBPB defenses.
Both Intel and AMD were informed of these vulnerabilities in June 2024. Intel acknowledged the issue and designated it as CVE-2023-38575, noting that a microcode fix had been released in March 2024. However, the researchers pointed out that this fix has not been universally implemented across all operating systems, including Ubuntu. AMD also confirmed the vulnerability, categorizing it as a software bug rather than a hardware flaw, which may explain its decision against issuing corrective microcode for the affected architectures.
As a response to these vulnerabilities, the ETH Zurich team is actively collaborating with Linux kernel maintainers to develop a patch specifically for the affected AMD processors. This work aims to enhance the security of Linux systems running on impacted Intel and AMD hardware, especially given that their research demonstrated the attacks could be effective even against the latest kernel versions with IBPB-on-entry defenses. The findings underscore the ongoing challenges in mitigating speculative execution vulnerabilities and the need for continuous updates to maintain cybersecurity resilience in modern computing environments.
