CVE-2023-31308 Overview
CVE-2023-31308 is an out-of-bounds memory read vulnerability affecting AMD System Management Unit (SMU) command handlers. A malicious virtual function can invoke certain SMU command handlers, triggering an out-of-bounds memory read that leads to a denial of service condition. The vulnerability is tracked under CWE-129: Improper Validation of Array Index and is documented in AMD Security Bulletin AMD-SB-6018.
Exploitation requires local access with low privileges and no user interaction. The impact is limited to availability, with no confidentiality or integrity consequences.
Critical Impact
An authenticated local attacker running a malicious virtual function can trigger a denial of service in the AMD SMU by invoking specific command handlers that read beyond allocated memory bounds.
Affected Products
- AMD processors implementing the affected System Management Unit (SMU) firmware — see AMD Security Bulletin AMD-SB-6018 for the complete affected product list
- Virtualization environments running on affected AMD hardware
- Systems executing untrusted virtual functions on affected AMD platforms
Discovery Timeline
- 2026-08-31 - CVE-2023-31308 published to the National Vulnerability Database (NVD)
- 2026-09-03 - Last updated in the NVD database
Technical Details for CVE-2023-31308
Vulnerability Analysis
The vulnerability resides in command handlers within the AMD System Management Unit (SMU). The SMU is a dedicated microcontroller embedded in AMD processors responsible for power management, thermal control, and platform coordination. Command handlers process requests submitted from higher privilege layers, including hypervisors and virtual functions.
When a malicious virtual function invokes certain SMU command handlers, the handler dereferences data outside its intended buffer boundary. The read operation touches memory locations that were never validated as part of the accepted command payload. This out-of-bounds access can crash the SMU state machine or produce inconsistent responses that halt platform coordination tasks.
Successful exploitation results in a denial of service condition affecting the availability of the platform management functions serviced by the SMU.
Root Cause
The root cause is improper validation of an array index [CWE-129] within the affected SMU command handlers. The handlers accept an index or offset from the caller and use it to reference memory without confirming the value falls within the expected range. When the index exceeds the allocated buffer, the handler reads adjacent memory, producing undefined behavior.
Attack Vector
The attack vector is local. An attacker requires low-privilege authenticated access on the host and the ability to execute a malicious virtual function that can dispatch commands to the SMU. No user interaction is required. Exploitation does not disclose data and does not modify system state; the observable outcome is loss of availability for SMU-serviced functionality.
Refer to AMD Security Bulletin AMD-SB-6018 for firmware-level technical details. No public proof-of-concept exploit is available for this vulnerability.
Detection Methods for CVE-2023-31308
Indicators of Compromise
- Unexpected SMU errors, hangs, or resets recorded in platform management logs and hypervisor event streams
- Repeated abnormal SMU command invocations originating from a specific guest or virtual function
- Sudden loss of power, thermal, or performance telemetry from the affected AMD platform
Detection Strategies
- Monitor hypervisor logs for anomalous SMU command patterns from guest virtual functions, particularly commands using out-of-range indices or offsets
- Baseline normal SMU command frequency per virtual function and alert on statistical deviations
- Correlate platform management interface (PMI) errors with tenant workload activity to identify malicious virtual functions
Monitoring Recommendations
- Ingest hypervisor, IPMI, and BMC logs into a centralized log platform for cross-correlation of SMU health indicators
- Track firmware version compliance across the AMD fleet against the fixed versions listed in AMD-SB-6018
- Alert on unexplained SMU resets or platform management timeouts, especially in multi-tenant virtualization environments
How to Mitigate CVE-2023-31308
Immediate Actions Required
- Inventory AMD processors and firmware versions in the environment and cross-reference against AMD Security Bulletin AMD-SB-6018
- Apply the SMU firmware and BIOS updates provided by AMD or the system OEM as soon as they are validated for the environment
- Restrict which tenants and workloads can create or deploy virtual functions on affected hosts until patches are applied
Patch Information
AMD has published fixed firmware guidance in AMD Security Bulletin AMD-SB-6018. Firmware updates are distributed through system OEMs as BIOS or platform microcode updates. Administrators should follow the OEM's guidance for staging and applying platform firmware in production environments.
Workarounds
- Limit local, low-privilege access to trusted operators until the firmware update is deployed
- Disable or restrict SR-IOV virtual functions on affected hosts where tenant isolation cannot be enforced
- Segregate untrusted workloads onto hardware that has already received the fixed AMD firmware
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
