CVE-2021-46749 in EPYC
Summary
by MITRE • 05/09/2023
Insufficient bounds checking in ASP (AMD Secure Processor) may allow for an out of bounds read in SMI (System Management Interface) mailbox checksum calculation triggering a data abort, resulting in a potential denial of service.
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Analysis
by VulDB Data Team • 01/28/2025
The vulnerability identified as CVE-2021-46749 resides within the AMD Secure Processor (ASP) component of AMD's processor architecture, specifically affecting the System Management Interface (SMI) mailbox checksum calculation mechanism. This flaw represents a critical security weakness that exploits insufficient bounds checking during data processing operations, creating a pathway for potential system compromise through denial of service attacks. The ASP serves as a dedicated security subsystem within AMD processors that handles sensitive operations including secure boot processes, firmware updates, and cryptographic functions, making its integrity paramount to overall system security.
The technical implementation of this vulnerability stems from inadequate input validation within the SMI mailbox handling routines where the ASP fails to properly verify array boundaries during checksum calculations. When malicious or malformed data is processed through the SMI interface, the insufficient bounds checking allows memory access beyond allocated buffer limits, triggering a data abort exception that results in system instability. This particular flaw operates at the hardware level within the secure processor's firmware, making it particularly challenging to detect and mitigate through traditional software-based security measures. The vulnerability manifests as an out-of-bounds read condition that can be exploited to cause system crashes or complete system hangs, effectively rendering the affected system unavailable to legitimate users.
From an operational perspective, this vulnerability poses significant risks to systems relying on AMD processors with secure processing capabilities, particularly in enterprise environments where system availability is critical. The potential for denial of service attacks through this mechanism can disrupt business operations and compromise system reliability, especially in scenarios where the ASP is responsible for critical security functions such as secure boot validation or firmware integrity checks. Attackers could potentially leverage this vulnerability to cause repeated system crashes, leading to service disruption that may require manual intervention and system restarts. The impact extends beyond simple availability concerns as the vulnerability may also provide attackers with opportunities to gather information about the system's memory layout or potentially escalate privileges through exploitation of the underlying secure processor architecture.
Mitigation strategies for CVE-2021-46749 should focus on firmware updates provided by AMD to address the bounds checking deficiencies within the ASP implementation. System administrators should prioritize applying official firmware patches and ensure that all systems utilizing AMD processors with secure processing capabilities are updated to versions that contain the necessary security fixes. Network segmentation and monitoring solutions should be implemented to detect unusual patterns of system instability or repeated system crashes that may indicate exploitation attempts. The vulnerability aligns with CWE-129 which addresses insufficient input validation and CWE-131 which covers incorrect calculation of buffer size, both of which are fundamental security principles that should be enforced in secure processor implementations. From an attack framework perspective, this vulnerability may be categorized under ATT&CK technique T1499.004 which covers network denial of service and potentially T1068 which involves exploit for privilege escalation, though the primary impact remains focused on availability disruption rather than privilege compromise. Organizations should also consider implementing runtime monitoring solutions that can detect abnormal memory access patterns and system abort conditions that may indicate exploitation attempts, while maintaining regular security assessments to identify other potential vulnerabilities within the secure processor subsystem.