CVE-2021-21556 Explained : Impact and Mitigation

Dell PowerEdge server BIOS versions less than 2.11.2 are affected by a stack-based buffer overflow vulnerability, allowing a local user with high privileges to exploit the system, potentially leading to denial of service, arbitrary code execution, or information disclosure.

Understanding CVE-2021-21556

This CVE pertains to a vulnerability in Dell PowerEdge BIOS that could be exploited by a local malicious user with high privileges, impacting the integrity and confidentiality of the system.

What is CVE-2021-21556?

The vulnerability in Dell PowerEdge server BIOS could result in a denial of service, arbitrary code execution, or information disclosure when exploited by a malicious local user with elevated privileges.

The Impact of CVE-2021-21556

The impact includes a medium severity base score of 6.1, with high confidentiality and integrity impacts. Attack complexity is low, with user interaction required.

Technical Details of CVE-2021-21556

This section covers the specific technical details of the CVE, including the vulnerability description, affected systems and versions, and exploitation mechanism.

Vulnerability Description

The vulnerability involves a stack-based buffer overflow in Dell PowerEdge BIOS on systems with NVDIMM-N installed, allowing potential exploitation by local users with high privileges.

Affected Systems and Versions

The affected product is the PowerEdge BIOS Intel 15G by Dell, with versions less than 2.11.2 being vulnerable to the exploit.

Exploitation Mechanism

A local malicious user with high privileges can exploit the vulnerability, potentially leading to denial of service, arbitrary code execution, or information disclosure within the UEFI or BIOS Preboot Environment.

Mitigation and Prevention

In this section, we cover the steps to mitigate and prevent the exploitation of CVE-2021-21556 on Dell PowerEdge servers.

Immediate Steps to Take

Immediate actions may include updating the BIOS to a secure version, restricting user access, and monitoring system activity for any signs of exploitation.

Long-Term Security Practices

Implementing security best practices, regular security audits, and ensuring timely patching of vulnerabilities are essential for long-term security.

Patching and Updates

Regularly checking for BIOS updates, installing security patches, and following Dell's security advisories are crucial for keeping systems secure.