CVE-2021-3808 Overview
CVE-2021-3808 is a high-severity vulnerability in the BIOS (UEFI Firmware) of certain HP PC products. The flaw could allow an attacker with local, low-privileged access to execute arbitrary code in the firmware execution environment. Because the vulnerability resides below the operating system, successful exploitation can compromise platform integrity, persist across OS reinstallations, and bypass standard endpoint defenses. HP released firmware updates across a wide range of business notebooks, workstations, desktops, all-in-ones, thin clients, and retail systems to address the issue. The CWE classification associated with this CVE is [CWE-269] Improper Privilege Management.
Critical Impact
A local attacker with low privileges can achieve arbitrary code execution in UEFI firmware, leading to full compromise of confidentiality, integrity, and availability of the affected system.
Affected Products
- HP EliteBook, ProBook, ZBook, and Elite Dragonfly notebook families across multiple generations (G3–G6)
- HP EliteDesk, ProDesk, EliteOne, ProOne desktops, workstations, and all-in-one business PCs
- HP Engage retail systems, MP9 G4 retail system, and HP mt21/mt31/mt44/mt45 mobile thin clients
Discovery Timeline
- 2023-02-01 - CVE-2021-3808 published to NVD
- 2025-03-27 - Last updated in NVD database
Technical Details for CVE-2021-3808
Vulnerability Analysis
The vulnerability exists in the UEFI firmware shipped on a broad set of HP commercial PC platforms. According to HP's advisory, the flaw could permit arbitrary code execution within the firmware boundary, an execution context that operates with higher privilege than the operating system kernel. The CWE-269 mapping indicates improper privilege management, suggesting that a code path within the firmware does not correctly enforce privilege separation between System Management Mode (SMM) or pre-boot firmware contexts and lower-privileged callers.
Attackers exploiting firmware-level flaws can install bootkits, tamper with Secure Boot policy, or persist malicious code in SPI flash. Such implants survive OS reinstallation and full disk wipes, making detection and remediation difficult.
Root Cause
The issue is rooted in improper privilege management within the affected BIOS/UEFI implementation. A privileged firmware interface accessible from the operating system fails to adequately validate the privilege level or input of the caller, allowing a low-privileged local actor to influence firmware execution.
Attack Vector
Exploitation requires local access to the target system and low-level privileges on the running operating system. The attacker does not need user interaction. Once code is staged on the host, the attacker can invoke the vulnerable firmware interface to escalate into the firmware execution context and run arbitrary code with platform-level privileges.
No public proof-of-concept code is available for this CVE, and HP has not disclosed exploitation primitives. Refer to the HP Security Advisory for vendor-confirmed details.
Detection Methods for CVE-2021-3808
Indicators of Compromise
- Unexpected modifications to SPI flash contents, UEFI variables, or Secure Boot databases (db, dbx, KEK, PK).
- BIOS version strings on affected models that do not match HP's fixed firmware versions listed in the advisory.
- Anomalous use of vendor BIOS update utilities or low-level flashing tools by non-administrator processes.
Detection Strategies
- Inventory firmware versions across the fleet using management tools and compare against HP's fixed versions for each affected model.
- Monitor for processes invoking SMI handlers, accessing \Device\PhysicalMemory, or interacting with WinFlash-style utilities from unexpected user contexts.
- Use firmware integrity attestation features such as Measured Boot and TPM PCR validation to identify deviations from a known-good baseline.
Monitoring Recommendations
- Centralize Windows event logs covering driver loads, kernel module activity, and privileged API usage to identify pre-exploitation behavior.
- Track endpoint telemetry for execution of unsigned or unexpected kernel drivers that could be used to reach the firmware interface.
- Establish alerts for changes to BIOS settings, BIOS administrator passwords, and firmware update events outside scheduled maintenance windows.
How to Mitigate CVE-2021-3808
Immediate Actions Required
- Identify all HP systems matching the affected product list and capture their current BIOS versions.
- Apply the firmware update published by HP for each affected platform as soon as practical, prioritizing devices used by privileged users.
- Restrict local administrative privileges on endpoints to reduce the population of users able to trigger the local attack vector.
Patch Information
HP has released firmware updates that mitigate this vulnerability across the impacted product families. Fixed BIOS versions vary by model and are enumerated in the HP Security Advisory. Customers should download the model-specific Softpaq from HP Support and deploy through standard firmware update channels such as HP Image Assistant, HP Manageability Integration Kit, or Microsoft Endpoint Configuration Manager.
Workarounds
- Set and enforce a strong BIOS administrator password to limit unauthorized firmware configuration changes.
- Enable HP Sure Start, Secure Boot, and TPM-based measured boot where supported to detect firmware tampering.
- Limit physical and remote local access to affected endpoints until the firmware update is applied.
# Configuration example: enumerate current BIOS version on Windows endpoints
wmic bios get smbiosbiosversion,manufacturer,releasedate
# Alternative using PowerShell
Get-CimInstance -ClassName Win32_BIOS | Select-Object Manufacturer, SMBIOSBIOSVersion, ReleaseDate
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
