CVE-2021-39299 Overview
CVE-2021-39299 is a UEFI firmware (BIOS) vulnerability affecting a wide range of HP PC products. This security flaw enables privilege escalation and arbitrary code execution at the firmware level, representing a significant threat to enterprise environments deploying affected HP hardware. UEFI/BIOS-level vulnerabilities are particularly dangerous as they can persist across operating system reinstallations and are difficult to detect with traditional security tools.
Critical Impact
Successful exploitation allows attackers to escalate privileges and execute arbitrary code at the firmware level, potentially compromising the entire system boot chain and persisting below the operating system.
Affected Products
- HP Elite Dragonfly, Elite Dragonfly G2, Elite Dragonfly Max
- HP EliteBook series (830, 836, 840, 846, 850, 1050 across G5-G8 generations)
- HP EliteBook x360 series (1030, 1040, 830 across G3-G8 generations)
- HP ProBook series (430, 440, 450, 470, 630, 640, 650 across G4-G8 generations)
- HP ZBook series (14u, 15, 15u, 17, Create, Firefly, Fury, Power, Studio)
- HP Z Workstation series (Z1, Z4, Z6, Z8)
- HP EliteDesk and ProDesk desktop series
- HP EliteOne and ProOne All-in-One series
- HP Engage and MP9 Retail Systems
Discovery Timeline
- February 16, 2022 - CVE-2021-39299 published to NVD
- November 21, 2024 - Last updated in NVD database
Technical Details for CVE-2021-39299
Vulnerability Analysis
This vulnerability resides within the UEFI firmware (BIOS) of numerous HP PC products. The flaw allows an attacker with local access to escalate privileges and execute arbitrary code within the firmware context. Exploitation requires local access to the system but does not require user interaction, making it suitable for post-compromise persistence scenarios.
The vulnerability affects the pre-boot environment, meaning malicious code can execute before the operating system loads. This provides attackers with the ability to install persistent implants that survive operating system reinstallation, bypass Secure Boot protections, and potentially intercept or modify the boot process. The scope is changed, meaning successful exploitation can affect resources beyond the vulnerable component's security authority.
Root Cause
The vulnerability stems from inadequate security controls within the UEFI firmware implementation. While the specific technical details have not been publicly disclosed by HP, UEFI vulnerabilities of this nature typically arise from insufficient input validation in SMM (System Management Mode) handlers, improper memory protection boundaries, or weaknesses in firmware update verification mechanisms that allow privilege escalation from ring 0 to SMM.
Attack Vector
The attack vector requires local access to the target system. An attacker with low-privilege access to the operating system can exploit this vulnerability to gain elevated privileges within the firmware layer. The attack flow typically involves:
- An attacker gains initial access to the target system with standard user privileges
- The attacker identifies a vulnerable HP system running affected UEFI firmware
- Exploitation of the vulnerability escalates privileges to the firmware/SMM level
- The attacker can then install persistent implants, modify boot components, or extract sensitive data stored in firmware
No verified proof-of-concept code is publicly available for this vulnerability. Organizations should refer to HP's Security Document for detailed technical information and affected firmware versions.
Detection Methods for CVE-2021-39299
Indicators of Compromise
- Unexpected modifications to UEFI firmware or BIOS configuration settings
- Changes to Secure Boot policies or certificate databases without authorized administrative action
- Anomalous SMM-related events in system firmware logs
- Presence of unknown or unsigned firmware modules during boot integrity checks
Detection Strategies
- Deploy firmware integrity monitoring solutions that validate BIOS/UEFI images against known-good baselines
- Enable and monitor TPM-based measured boot to detect unauthorized firmware modifications
- Implement SentinelOne's firmware protection capabilities to detect pre-boot threats
- Conduct regular firmware version audits to identify systems running vulnerable BIOS versions
Monitoring Recommendations
- Configure centralized logging for firmware update events and BIOS configuration changes
- Monitor for attempts to access SMM-related resources or trigger SMI (System Management Interrupt) handlers
- Implement hardware inventory management to track firmware versions across the enterprise
- Establish alerting for any systems failing Secure Boot attestation
How to Mitigate CVE-2021-39299
Immediate Actions Required
- Identify all HP systems in your environment that are affected by this vulnerability using the comprehensive product list in HP's advisory
- Prioritize patching for systems containing sensitive data or operating in high-security environments
- Enable Secure Boot and configure BIOS passwords to prevent unauthorized firmware modifications
- Apply firmware updates during scheduled maintenance windows with proper change management procedures
Patch Information
HP has released updated UEFI firmware to address this vulnerability. Administrators should consult HP's Security Document to obtain the specific firmware versions that remediate this vulnerability for each affected product. Firmware updates should be applied using HP's official tools such as HP Image Assistant (HPIA) or HP Client Management Script Library (CMSL) for enterprise deployments.
Workarounds
- Enable BIOS administrator passwords to prevent unauthorized firmware modifications
- Configure Secure Boot with custom keys to establish stronger boot chain verification
- Restrict physical access to affected systems where possible
- Implement network segmentation to limit lateral movement if a system is compromised
- Consider disabling unused firmware features (e.g., PXE boot, USB boot) in BIOS settings to reduce attack surface
# Example: Using HP Image Assistant (HPIA) for firmware deployment
# Download HPIA from HP support and run with appropriate parameters
HPImageAssistant.exe /Operation:Analyze /Category:BIOS /Selection:All /Action:List /ReportFolder:C:\HPIA_Reports
# Review report for firmware updates, then apply:
HPImageAssistant.exe /Operation:Analyze /Category:BIOS /Selection:All /Action:Install /Silent
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
