CVE-2023-39539 Overview
CVE-2023-39539 is a BIOS/UEFI vulnerability in AMI AptioV that allows an authenticated local user to upload a malicious PNG logo file with dangerous type properties. This unrestricted file upload vulnerability in the BIOS firmware can be exploited to achieve arbitrary code execution at the firmware level, potentially compromising the entire system before the operating system even loads.
Critical Impact
Successful exploitation may lead to complete loss of Confidentiality, Integrity, and Availability at the firmware level, enabling persistent malware that survives OS reinstallation.
Affected Products
- AMI AptioV BIOS Firmware (all versions prior to patched release)
- Systems utilizing AMI AptioV UEFI firmware
- NetApp products utilizing affected AMI firmware (see NTAP-20240105-0003)
Discovery Timeline
- 2023-12-06 - CVE-2023-39539 published to NVD
- 2024-11-21 - Last updated in NVD database
Technical Details for CVE-2023-39539
Vulnerability Analysis
This vulnerability stems from improper input validation (CWE-20) and unrestricted upload of dangerous file types (CWE-434) within the AMI AptioV BIOS firmware. The BIOS logo customization feature allows users to upload PNG image files for boot splash screens, but fails to properly validate the contents and type of uploaded files.
An attacker with local access and low privileges can exploit this weakness to upload a specially crafted PNG file that contains malicious payloads. Because this occurs at the firmware level, successful exploitation grants the attacker the highest level of system access, operating below the operating system and any security software.
The local attack vector requires physical or privileged local access to the system, but once exploited, the impact is severe across all three security dimensions: confidentiality, integrity, and availability.
Root Cause
The root cause is insufficient validation of uploaded PNG logo files in the BIOS setup utility. The firmware fails to properly verify that uploaded files conform to expected PNG specifications and contain only legitimate image data. This allows attackers to embed executable code or trigger memory corruption through malformed image headers or embedded payloads within what appears to be a legitimate logo file.
Attack Vector
The attack requires local access to the BIOS setup interface or a privileged process that can interact with the firmware update mechanisms. An attacker must:
- Gain local access to the target system with low-level privileges
- Access the BIOS logo customization feature
- Upload a specially crafted PNG file containing malicious payload
- The firmware processes the malicious file without proper validation
- Code execution occurs at the firmware level, below the operating system
The vulnerability is particularly dangerous because firmware-level compromise persists across operating system reinstallations and can be used to establish a highly persistent backdoor or rootkit.
Detection Methods for CVE-2023-39539
Indicators of Compromise
- Unexpected modifications to BIOS logo or splash screen images
- Changes to BIOS/UEFI firmware timestamps or checksums
- Unusual BIOS configuration changes not authorized by administrators
- Failed firmware integrity checks during secure boot validation
Detection Strategies
- Implement firmware integrity monitoring to detect unauthorized BIOS modifications
- Enable Secure Boot and monitor for integrity validation failures
- Use hardware-based attestation mechanisms (TPM) to verify firmware state
- Deploy endpoint detection solutions capable of firmware-level monitoring
Monitoring Recommendations
- Regularly audit BIOS/UEFI settings and compare against known-good baselines
- Monitor for privileged local access attempts that could precede BIOS modification
- Implement alerting for any firmware update or configuration change events
- Review system event logs for BIOS-related errors or unexpected reboots
How to Mitigate CVE-2023-39539
Immediate Actions Required
- Apply firmware updates from AMI or your system vendor immediately
- Restrict physical and local privileged access to affected systems
- Enable BIOS password protection to prevent unauthorized configuration changes
- Verify Secure Boot is enabled and properly configured on all affected systems
Patch Information
AMI has released a security advisory addressing this vulnerability. System administrators should consult the AMI Security Advisory AMI-SA-2023009 for specific patch information and updated firmware versions. NetApp customers should also review the NetApp Security Advisory NTAP-20240105-0003 for guidance on affected NetApp products. Additional technical information is available from CERT Vulnerability Note VU#811862.
Contact your hardware vendor for platform-specific BIOS updates that incorporate the AMI security fixes.
Workarounds
- Disable BIOS logo customization features if not required for business operations
- Implement strict physical access controls to prevent unauthorized local access
- Use BIOS passwords and enable administrator locks on firmware settings
- Enable Secure Boot to help detect unauthorized firmware modifications
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
