CVE-2021-46792 : Vulnerability Insights and Analysis

CVE-2021-46792 is a vulnerability affecting multiple AMD processors that can result in a denial of service due to a race condition in the BIOS2PSP command. The flaw may allow an attacker with a malicious BIOS to exploit Time-of-check Time-of-use (TOCTOU) vulnerabilities.

Understanding CVE-2021-46792

What is CVE-2021-46792?

Time-of-check Time-of-use (TOCTOU) in the BIOS2PSP command may allow an attacker with a malicious BIOS to create a race condition, causing the ASP bootloader to perform out-of-bounds SRAM reads upon an S3 resume event, potentially leading to a denial of service.

The Impact of CVE-2021-46792

Vulnerability in multiple AMD processors
Potential denial of service due to a race condition
Exploitation of TOCTOU vulnerabilities

Technical Details of CVE-2021-46792

Vulnerability Description

The TOCTOU vulnerability in the BIOS2PSP command can enable attackers with a malicious BIOS to trigger a race condition, potentially causing the ASP bootloader to conduct out-of-bounds SRAM reads during an S3 resume event, leading to a denial of service.

Affected Systems and Versions

Affected processors include Ryzen™ 2000 series, Ryzen™ 5000 series, Athlon™ 3000 series, and more.
Various versions of AGESA are impacted.

Exploitation Mechanism

The exploit revolves around manipulating the BIOS2PSP command to create a race condition, leveraging TOCTOU to induce out-of-bounds SRAM reads during an S3 resume event.

Mitigation and Prevention

Immediate Steps to Take

Update the BIOS to the latest version provided by AMD.
Implement BIOS security best practices.

Long-Term Security Practices

Regularly check for BIOS updates and security advisories.
Employ secure boot mechanisms and BIOS protections.

Patching and Updates

AMD has provided patches and updates to address CVE-2021-46792.