CVE-2021-3808 Overview
CVE-2021-3808 is a BIOS/UEFI firmware vulnerability affecting a wide range of HP PC products. The vulnerability exists within the UEFI firmware implementation and could allow an attacker with local access to execute arbitrary code at the firmware level. UEFI firmware vulnerabilities are particularly concerning as they operate below the operating system, potentially enabling persistent malware that survives OS reinstallation and traditional security tools.
Critical Impact
Successful exploitation allows arbitrary code execution at the firmware level, enabling attackers to establish persistent system compromise that persists across operating system reinstalls and can bypass traditional security controls.
Affected Products
- HP Elite Dragonfly, Elite X2 series (G2, G3, G4)
- HP EliteBook series (725, 735, 745, 755, 820, 828, 830, 836, 840, 846, 848, 850 generations G4-G6)
- HP EliteBook X360 series (1020, 1030, 1040, 830 generations G2-G6)
- HP ProBook series (430, 440, 445, 450, 455, 470, 640, 645, 650, 655 generations G3-G6)
- HP ZBook series (14u, 15, 15u, 17, Studio, X2 generations G4-G6)
- HP EliteDesk, ProDesk, EliteOne, ProOne desktop systems
- HP Z Workstation series (Z1, Z2, Z238, Z240)
- HP Mobile Thin Clients (MT21, MT31, MT44, MT45)
- HP Engage Retail Systems
Discovery Timeline
- February 1, 2023 - CVE-2021-3808 published to NVD
- March 27, 2025 - Last updated in NVD database
Technical Details for CVE-2021-3808
Vulnerability Analysis
This vulnerability resides in the BIOS (UEFI Firmware) of affected HP PC products. The flaw enables arbitrary code execution at the firmware level, which represents one of the most privileged execution contexts on modern PC systems. Firmware-level code execution is particularly dangerous because UEFI runs before the operating system loads and has direct hardware access.
The vulnerability requires local access to exploit, meaning an attacker would need either physical access to the system or an existing foothold through another compromise vector. Once exploited, the attacker can execute code with System Management Mode (SMM) privileges or similar high-privilege firmware contexts. This can lead to complete system compromise, including the ability to install persistent malware (bootkits/rootkits) that traditional security solutions cannot detect or remediate.
The CWE-269 classification (Improper Privilege Management) suggests the vulnerability stems from inadequate privilege separation or validation within the firmware's handling of certain operations.
Root Cause
The vulnerability is classified under CWE-269 (Improper Privilege Management), indicating that the UEFI firmware fails to properly manage privilege boundaries. This likely involves insufficient validation or improper access controls that allow lower-privileged code paths to execute operations that should be restricted to higher-privilege firmware contexts.
UEFI firmware vulnerabilities commonly arise from issues such as improper validation of System Management Interrupt (SMI) handlers, insecure handling of UEFI variables, or flaws in firmware update mechanisms that can be abused to inject malicious code.
Attack Vector
The attack requires local access to the affected system. An attacker would need to execute malicious code on the target system first, then leverage this vulnerability to elevate privileges to the firmware level. The attack flow typically involves:
- Gaining initial local access through social engineering, physical access, or exploiting another vulnerability
- Triggering the vulnerable firmware code path through crafted system calls or by manipulating UEFI variables
- Achieving arbitrary code execution within the privileged firmware context
- Installing persistent malicious firmware modifications or extracting sensitive data
The local attack vector combined with low privileges required makes this vulnerability exploitable by any user with local system access, though the technical complexity of firmware exploitation typically requires specialized knowledge.
Detection Methods for CVE-2021-3808
Indicators of Compromise
- Unexpected modifications to UEFI firmware variables or settings not initiated by authorized personnel
- System boot anomalies such as extended POST times or unexpected boot behavior
- Firmware version discrepancies between reported and expected versions
- Presence of unauthorized UEFI modules or drivers in the firmware image
Detection Strategies
- Implement firmware integrity monitoring using HP Sure Start or similar hardware-assisted firmware verification technologies
- Deploy endpoint detection and response (EDR) solutions capable of monitoring firmware-level activities and UEFI variable access
- Conduct regular firmware inventory audits comparing installed versions against known vulnerable firmware versions listed in HP's security bulletin
- Monitor system logs for unusual SMI (System Management Interrupt) activity or UEFI runtime service calls
Monitoring Recommendations
- Enable HP Sure Start or equivalent firmware protection features where available on affected systems
- Implement centralized logging of firmware update events and BIOS configuration changes
- Deploy SentinelOne agents with firmware monitoring capabilities to detect anomalous firmware-level activities
- Establish baseline firmware configurations and alert on any deviations
How to Mitigate CVE-2021-3808
Immediate Actions Required
- Inventory all HP systems in your environment and identify affected models using the comprehensive list in the HP Security Bulletin
- Prioritize firmware updates for systems handling sensitive data or in high-security environments
- Restrict local administrative access to affected systems until patches can be applied
- Enable HP Sure Start and other hardware-based security features to provide defense-in-depth protection
Patch Information
HP has released firmware updates to address this vulnerability. Administrators should download and apply the appropriate BIOS update for each affected model from HP's official support portal. The specific firmware versions that remediate this vulnerability vary by product model and are detailed in the HP Security Bulletin HPSBHF03788.
Firmware updates should be applied following HP's recommended procedures, including:
- Backing up current BIOS settings before updating
- Ensuring systems are connected to reliable power during the update process
- Following HP's firmware update utility instructions for each specific model
Workarounds
- Enable BIOS administrator passwords to prevent unauthorized firmware configuration changes
- Configure UEFI Secure Boot to help prevent unauthorized firmware and bootloader modifications
- Implement physical security controls to limit unauthorized local access to affected systems
- Use HP Sure Admin or similar remote BIOS management tools to enforce firmware security policies across the enterprise
# HP firmware update verification example
# After updating, verify firmware version matches patched release
# Check current BIOS version on Windows systems
wmic bios get smbiosbiosversion
# On Linux systems, check BIOS version using dmidecode
dmidecode -s bios-version
# Compare against patched versions listed in HP Security Bulletin HPSBHF03788
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
