CVE-2023-20576 in Ryzen 3000 Desktop Processors
Summary
by MITRE • 09/02/2026
Insufficient Verification of Data Authenticity in AGESA™ may allow an attacker to update SPI ROM data potentially resulting in denial of service or privilege escalation.
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Analysis
by VulDB Data Team • 09/02/2026
The vulnerability identified within the AMD Generic Encapsulated Software Architecture, commonly referred to as AGESA, represents a critical failure in the integrity verification mechanisms governing system firmware updates. Specifically, this flaw resides in the process responsible for handling Serial Peripheral Interface Read-Only Memory data during update operations. The core technical deficiency is an insufficient verification of data authenticity, which means that the software component fails to adequately validate cryptographic signatures or checksums before accepting and writing new code into the SPI flash memory chips that store BIOS and UEFI firmware. This lack of rigorous authentication allows malicious actors who have gained access to the system's update mechanisms to inject unauthorized modifications into the firmware layer without detection by standard security controls designed to prevent tampering with low-level system software.
From an operational perspective, this vulnerability enables a range of severe attacks depending on the attacker's position and capabilities. If an adversary can manipulate the SPI ROM data during an update process or exploit a side-channel attack vector that allows them to alter stored firmware images, they effectively bypass traditional operating system security boundaries. The immediate consequence is often a denial of service condition where the system fails to boot correctly due to corrupted or incompatible firmware instructions. However, the more dangerous implication involves privilege escalation. By modifying specific regions of the SPI ROM, an attacker can implant malicious code that executes with higher privileges than standard user applications, potentially achieving kernel-level access before the operating system even initializes. This effectively compromises the entire trust chain of the computing platform, as firmware runs at a level above the OS and hypervisor in most modern architectures.
This flaw aligns closely with CWE-345 Insufficient Verification of Data Authenticity, which describes scenarios where software does not verify that data has been tampered with or is from an untrusted source before processing it. In the context of firmware security, this failure undermines the fundamental principle of secure boot and trusted platform modules that rely on immutable base code to ensure system integrity. Furthermore, in terms of offensive cyber operations mapping, this vulnerability facilitates techniques associated with MITRE ATT&CK ID T1509 Firmware Corruption or T1623 Privilege Escalation via Bootkit mechanisms. Attackers can leverage this weakness to establish persistent backdoors that survive operating system reinstalls and standard security patches, making remediation extremely difficult without specialized hardware tools for firmware reflashing.
Mitigation strategies must focus on strengthening the cryptographic validation processes within the AGESA implementation. Vendors should ensure that all SPI ROM updates are signed using strong asymmetric cryptography with keys managed through a secure key management infrastructure. Additionally, implementing measured boot processes where each stage of firmware execution is verified against known good hashes before proceeding can prevent unauthorized code from executing even if it is written to memory. System administrators and enterprise IT departments should restrict physical access to devices containing vulnerable AGESA versions and ensure that only authorized, digitally signed firmware updates are applied through automated management tools rather than manual interventions. Regular auditing of firmware integrity using hardware-based root-of-trust solutions can also help detect any unauthorized modifications post-deployment.