CVE-2023-20576 Overview
CVE-2023-20576 is a firmware vulnerability in AMD Generic Encapsulated Software Architecture (AGESA™). The flaw stems from insufficient verification of data authenticity [CWE-345] during SPI ROM update operations. An attacker with local access can modify SPI ROM contents without proper cryptographic validation. Successful exploitation may lead to denial of service or privilege escalation on affected AMD platforms. The vulnerability affects the firmware initialization layer that platform BIOS implementations build upon. AMD published details in Security Bulletin SB-7009.
Critical Impact
Local attackers can tamper with SPI ROM data, enabling persistent firmware compromise, denial of service, or elevation to privileged execution contexts below the operating system.
Affected Products
- AMD AGESA™ firmware reference code
- AMD platforms integrating vulnerable AGESA versions
- OEM system BIOS builds derived from affected AGESA releases
Discovery Timeline
- 2026-09-02 - CVE-2023-20576 published to NVD
- 2026-09-02 - Last updated in NVD database
Technical Details for CVE-2023-20576
Vulnerability Analysis
The vulnerability resides in AGESA™, the foundational firmware reference code AMD provides to platform manufacturers. AGESA initializes CPU, memory, and chipset components during early boot. Within this code path, logic that handles SPI ROM update operations does not adequately verify the authenticity of incoming data. An attacker who reaches the vulnerable code path can supply data that the firmware accepts as legitimate.
SPI ROM stores platform firmware, including UEFI code executed before the operating system loads. Modifications to SPI ROM contents persist across reboots and operate outside the trust boundary of the operating system. Because the attack requires local access with low complexity and no user interaction, an authenticated local process can attempt exploitation directly.
Root Cause
The root cause is a missing or insufficient integrity check on SPI ROM update payloads. CWE-345 describes weaknesses where software does not sufficiently verify the origin or authenticity of data. In this case, the firmware fails to enforce a cryptographic signature verification or equivalent authenticity control before committing changes to non-volatile storage.
Attack Vector
Exploitation requires local access to the target system. An attacker running code on the host, potentially with elevated privileges obtained through a separate vector, invokes the SPI ROM update path and supplies crafted data. The firmware accepts the payload without confirming authenticity. The resulting write can corrupt firmware to trigger denial of service or introduce code that executes with firmware-level privileges on subsequent boots.
No verified public exploit is available at the time of publication. Refer to the AMD Security Bulletin SB-7009 for platform-specific technical details.
Detection Methods for CVE-2023-20576
Indicators of Compromise
- Unexpected changes to SPI flash contents measured against a known-good baseline
- BIOS or UEFI version strings that do not match the vendor-supplied build for the platform
- Platform firmware measurements in TPM PCRs that deviate from expected values after boot
Detection Strategies
- Compare SPI ROM images captured offline against manufacturer-signed reference images
- Use platform attestation and measured boot data to identify firmware drift across the fleet
- Monitor for local processes that interact with SPI flash programming interfaces or flashrom-style utilities
Monitoring Recommendations
- Enable and centrally collect UEFI Secure Boot and measured boot telemetry from endpoints
- Alert on privileged local operations that access chipset SPI controllers outside authorized firmware update windows
- Track BIOS version inventory across systems and flag unauthorized downgrades or unsigned updates
How to Mitigate CVE-2023-20576
Immediate Actions Required
- Identify AMD-based systems in your environment and cross-reference them with the affected platform list in AMD Security Bulletin SB-7009
- Apply the AGESA-based BIOS update supplied by the system or motherboard vendor as soon as it is available
- Restrict local administrative access on affected systems to reduce opportunities to reach the vulnerable code path
Patch Information
AMD has published fixes in updated AGESA firmware. Because AGESA is delivered to end users through OEM and motherboard vendor BIOS releases, obtain the corresponding BIOS update from the platform manufacturer. Consult the AMD Security Bulletin SB-7009 for the list of affected products and fixed AGESA versions.
Workarounds
- Enforce full-disk and platform-level access controls to prevent unauthorized local code execution
- Enable BIOS write protection, chassis intrusion detection, and administrator BIOS passwords where supported
- Require signed firmware updates and disable legacy or unauthenticated flashing paths in BIOS setup
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
