AMD has revealed four new vulnerabilities that could enable attackers to access sensitive data via timing-based side-channel attacks. These vulnerabilities, called AMD-SB-7029 or Transient Scheduler Attacks, impact various AMD processors, including EPYC chips for data centers and Ryzen processors for enterprises.
The recent disclosure has ignited a debate over threat severity ratings. CrowdStrike, a top cybersecurity firm, labels key vulnerabilities as “critical,” while AMD rates them as medium and low. This disagreement shows the difficulties companies encounter in assessing processor security risks.
The company started issuing Platform Initialization firmware updates to OEMs and is working with OS vendors on complete solutions.
The vulnerabilities emerged from AMD’s investigation of a Microsoft research report titled “Enter, Exit, Page Fault, Leak: Testing Isolation Boundaries for Microarchitectural Leaks.” AMD discovered what it calls “transient scheduler attacks related to the execution timing of instructions under specific microarchitectural conditions.”
These attacks take advantage of “false completions” in CPU operations. When CPUs anticipate quick load instruction completions but face obstacles, attackers can analyze timing variations to gain sensitive information.
“In some cases, an attacker may be able to use this timing information to infer data from other contexts, resulting in information leakage,” AMD stated in its security bulletin.
AMD has discovered two types of attacks that businesses need to be aware of. TSA-L1 attacks exploit mistakes in L1 cache microtag lookups, which can lead to improper data loading that attackers may notice. TSA-SQ attacks happen when load instructions mistakenly pull data from the store queue when the needed data is missing, which could let attackers infer sensitive information from past operations, according to the bulletin.
The scope of affected systems presents significant challenges for enterprise patch management teams. Vulnerable processors include 3rd and 4th generation EPYC processors powering cloud and on-premises data center infrastructure, Ryzen series processors deployed across corporate workstation environments, and enterprise mobile processors supporting remote and hybrid work arrangements.
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