CVE-2021-26402 : Vulnerability Insights and Analysis

A detailed overview of CVE-2021-26402, including its impact, technical details, and mitigation strategies.

Understanding CVE-2021-26402

CVE-2021-26402 is a security vulnerability found in AMD Secure Processor (ASP) firmware, specifically in the handling of BIOS mailbox commands.

What is CVE-2021-26402?

The vulnerability stems from insufficient bounds checking in ASP firmware, which could allow an attacker to write partially-controlled data out-of-bounds to System Management Mode (SMM) or Secure Encrypted Virtualization Encrypted State (SEV-ES) regions. This exploit may result in a potential loss of data integrity and availability.

The Impact of CVE-2021-26402

The exploitation of this vulnerability could lead to unauthorized modification of data in critical regions, compromising the overall system's security and potentially enabling attackers to execute arbitrary code.

Technical Details of CVE-2021-26402

This section covers a detailed analysis of the vulnerability, affected systems, and the exploitation mechanism.

Vulnerability Description

The vulnerability arises due to the lack of proper bounds checking in ASP firmware while processing BIOS mailbox commands, enabling attackers to write data outside of the designated boundaries.

Affected Systems and Versions

The vulnerability affects AMD platforms, particularly the 2nd Gen EPYC and 3rd Gen EPYC products running various versions of the AGESA firmware.

Exploitation Mechanism

By exploiting this vulnerability, malicious actors can craft specific data payloads to write beyond the allowed memory boundaries, potentially accessing and tampering with critical system regions.

Mitigation and Prevention

Outlined below are the steps to mitigate the impact of CVE-2021-26402 and prevent potential security breaches.

Immediate Steps to Take

Apply security patches and updates provided by AMD to address the vulnerability in the ASP firmware.
Monitor system logs and behavior for any suspicious activities that may indicate exploitation attempts.

Long-Term Security Practices

Regularly update and maintain firmware and software to ensure the latest security patches are in place.
Implement access controls and authentication mechanisms to restrict unauthorized access to critical system components.
Conduct regular security audits and assessments to identify and remediate vulnerabilities proactively.

Patching and Updates

AMD has released security advisory AMD-SB-1032 detailing the vulnerability and providing patches. Refer to the vendor advisory link for specific guidance on updating affected systems.