CVE-2021-33124 in Intel
Summary
by MITRE • 05/12/2022
Out-of-bounds write in the BIOS authenticated code module for some Intel(R) Processors may allow a privileged user to potentially enable aescalation of privilege via local access.
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Analysis
by VulDB Data Team • 05/16/2022
The vulnerability identified as CVE-2021-33124 represents a critical out-of-bounds write flaw within the BIOS authenticated code module of certain Intel processors. This issue resides in the firmware layer that governs the secure boot process and code execution verification, making it particularly dangerous as it operates at the lowest level of system security. The vulnerability affects Intel processors that implement specific BIOS authenticated code modules, which are responsible for verifying the integrity of code before execution during the boot process. The flaw stems from improper bounds checking within the authenticated code module, allowing malicious code to write data beyond the allocated memory boundaries.
The technical nature of this vulnerability places it squarely within the CWE-787 category of out-of-bounds write conditions, which occur when a program writes to memory locations outside the boundaries of a buffer. This particular flaw manifests in the BIOS authenticated code execution environment where privileged users can exploit the insufficient validation of input parameters. The vulnerability requires local access to exploit, meaning an attacker must already have some level of system access, but the privilege escalation potential is significant since it operates within the trusted BIOS environment. The authenticated code module is designed to ensure only verified and trusted code executes, making this flaw particularly concerning as it undermines the fundamental security assumptions of the boot process.
The operational impact of CVE-2021-33124 extends beyond simple privilege escalation to potentially compromise the entire system security posture. When successfully exploited, the vulnerability allows a privileged user to gain elevated privileges that would normally be restricted, effectively breaking the security model that protects against unauthorized access. This could enable attackers to bypass secure boot mechanisms, modify system firmware, or execute arbitrary code with the highest system privileges. The implications are severe because BIOS-level exploits can persist across operating system reboots and are difficult to detect or remediate. The vulnerability affects systems where Intel processors implement specific authenticated code modules, particularly those used in enterprise environments where system integrity is paramount and where the risk of persistent malware installation is significant.
Mitigation strategies for CVE-2021-33124 focus primarily on firmware updates from Intel and system vendors, as the vulnerability exists within the BIOS code itself. Organizations should immediately apply the latest BIOS updates provided by Intel and their hardware vendors to address the bounds checking issue within the authenticated code module. System administrators should also implement additional monitoring and logging around BIOS code execution and boot processes to detect potential exploitation attempts. The vulnerability aligns with ATT&CK technique T1014 where adversaries may use BIOS or UEFI firmware modifications to maintain persistence. Network segmentation and access controls should be reinforced to limit local access privileges, as the vulnerability requires local system access for exploitation. Regular firmware integrity verification should be implemented alongside traditional security controls to ensure the authenticated code module remains uncorrupted and that the system maintains its intended security posture throughout its operational lifecycle.