CVE-2023-20555 : What You Need to Know

This CVE record was published on August 8, 2023, by AMD, affecting multiple processors in their product lineup.

Understanding CVE-2023-20555

This CVE-2023-20555 pertains to a vulnerability in the AGESA container in various AMD processors, potentially leading to arbitrary code execution in System Management Mode (SMM).

What is CVE-2023-20555?

The vulnerability involves insufficient input validation in CpmDisplayFeatureSmm, which could allow an attacker to corrupt SMM memory by overwriting an arbitrary bit in an attacker-controlled pointer. This could result in the execution of arbitrary code in SMM.

The Impact of CVE-2023-20555

As a critical vulnerability, CVE-2023-20555 poses a high risk as it could be exploited by attackers to gain unauthorized access to the affected systems and execute malicious code in SMM, a privileged operating mode with significant control over the system.

Technical Details of CVE-2023-20555

This section delves into the specifics of the vulnerability, including its description, affected systems and versions, as well as the exploitation mechanism.

Vulnerability Description

The vulnerability in CpmDisplayFeatureSmm allows attackers to corrupt SMM memory by manipulating an attacker-controlled pointer, potentially enabling them to execute arbitrary code within the privileged SMM environment.

Affected Systems and Versions

The issue impacts a range of AMD processors, including the Ryzen, Athlon, and mobile processor series, running various versions of AGESA firmware.

Exploitation Mechanism

Attackers can exploit this vulnerability by leveraging insufficient input validation in CpmDisplayFeatureSmm to overwrite specific memory addresses within SMM, ultimately gaining the ability to execute arbitrary code with elevated privileges.

Mitigation and Prevention

To safeguard systems against the risks associated with CVE-2023-20555, immediate actions and long-term security measures should be implemented.

Immediate Steps to Take

Organizations should apply any available patches or security updates provided by AMD to address the vulnerability promptly.
Monitor for any unusual or suspicious activities that could indicate an ongoing exploitation attempt.

Long-Term Security Practices

Regularly update firmware and software to ensure that systems are equipped with the latest security enhancements.
Implement robust security protocols, such as restricting access privileges and employing strong authentication mechanisms.

Patching and Updates

AMD has released a security advisory (AMD-SB-4003) detailing the vulnerability and providing guidance on how to mitigate the risks associated with CVE-2023-20555. Organizations are advised to refer to the advisory and apply the necessary patches to secure their systems.