CVE-2021-39297: HP 260 G3 UEFI Privilege Escalation Flaw

CVE-2021-39297 Overview

CVE-2021-39297 is a vulnerability identified in UEFI firmware (BIOS) affecting a wide range of HP PC products. This firmware-level security flaw allows local attackers with low privileges to escalate their privileges and execute arbitrary code at the highest system privilege level. The vulnerability affects the foundational boot firmware of HP enterprise desktops, workstations, notebooks, and retail systems, making it particularly concerning for organizations deploying HP hardware infrastructure.

UEFI firmware vulnerabilities represent a significant security risk because they operate below the operating system level, potentially allowing attackers to persist across OS reinstallations and evade traditional security controls. Successful exploitation of this vulnerability could enable attackers to install persistent malware, bypass security features like Secure Boot, and gain complete control over affected systems.

Critical Impact

Local attackers can exploit this UEFI firmware vulnerability to escalate privileges and execute arbitrary code with system-level access, potentially compromising the entire boot chain and enabling persistent, undetectable malware installation.

Affected Products

• HP EliteDesk 800 Series (G4, G5, G6, G8 variants including Desktop Mini, Tower, and Small Form Factor PCs)
• HP EliteBook Series (830, 840, 850, 1050, x360 models across G5-G8 generations)
• HP ProDesk Series (400, 480, 600, 680 models across G4-G8 generations)
• HP ProBook Series (430, 440, 450, 470, 630, 640, 650 models across G4-G8 generations)
• HP ZBook Series (14u, 15, 15u, 17, Create, Firefly, Fury, Power, Studio models)
• HP Z Workstation Series (Z1, Z4, Z6, Z8 G4-G8)
• HP Elite Dragonfly Series (original, G2, Max)
• HP Elite x2 Tablets (1013 G3, G4, G8)
• HP ProOne All-in-One Series (400, 440, 600 models)
• HP EliteOne All-in-One Series (800, 1000 models)
• HP Engage Flex Mini and MP9 G4 Retail Systems
• HP Zhan 66 Pro Series (notebooks and all-in-one PCs)

Discovery Timeline

• February 16, 2022 - CVE-2021-39297 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2021-39297

Vulnerability Analysis

This vulnerability resides in the UEFI firmware implementation across HP's extensive PC product portfolio. The flaw enables privilege escalation from a low-privileged local context to system-level execution, with the ability to execute arbitrary code within the firmware environment. The vulnerability's scope extends beyond the vulnerable component itself, meaning exploitation can impact resources beyond the firmware's normal boundaries.

The local attack vector requires an attacker to have some level of access to the target system, but the low privilege requirement and absence of user interaction makes exploitation feasible once initial access is obtained. The potential for complete compromise of confidentiality, integrity, and availability at the firmware level makes this a significant threat to enterprise security postures.

Root Cause

The vulnerability stems from security weaknesses in the UEFI firmware code that fail to properly validate or restrict operations at the firmware level. UEFI firmware operates with the highest system privileges and controls the boot process, hardware initialization, and system configuration. Improper security controls within this firmware layer allow unauthorized privilege escalation and code execution capabilities.

Attack Vector

An attacker with local access and low privileges can exploit this vulnerability without requiring user interaction. The attack flow involves:

1. The attacker gains initial local access to an affected HP system with low-level user privileges
2. The attacker crafts malicious input or leverages specific firmware interfaces to trigger the vulnerability
3. Upon successful exploitation, the attacker gains elevated privileges within the UEFI firmware environment
4. The attacker can then execute arbitrary code at the firmware level, potentially installing persistent implants that survive OS reinstallation

The firmware-level nature of this vulnerability means traditional operating system security controls are ineffective once exploitation occurs. Attackers could disable Secure Boot protections, install bootkits, or modify system firmware to maintain persistent access.

Detection Methods for CVE-2021-39297

Indicators of Compromise

• Unexpected BIOS/UEFI firmware version changes or modifications to firmware settings
• Secure Boot configuration changes or disabled Secure Boot without administrative action
• Anomalous system behavior during boot sequence or unexpected UEFI shell access
• Firmware integrity check failures reported by HP Sure Start or similar firmware protection features

Detection Strategies

• Implement firmware integrity monitoring using HP Sure Start or similar UEFI protection technologies
• Enable and monitor Trusted Platform Module (TPM) measurements to detect unauthorized firmware modifications
• Deploy endpoint detection and response (EDR) solutions with firmware-level visibility capabilities
• Monitor for unauthorized local privilege escalation attempts or suspicious system management mode (SMM) activity

Monitoring Recommendations

• Regularly audit BIOS/UEFI firmware versions across the enterprise against HP's published secure versions
• Enable firmware event logging and integrate logs with SIEM solutions for centralized monitoring
• Implement baseline firmware configuration management and alert on deviations
• Monitor for suspicious access to firmware update utilities or UEFI runtime services

How to Mitigate CVE-2021-39297

Immediate Actions Required

• Inventory all HP systems in your environment to identify affected models from the extensive product list
• Prioritize firmware updates for systems handling sensitive data or critical business functions
• Restrict local access to affected systems until firmware updates can be applied
• Enable HP Sure Start and Secure Boot where available to provide additional firmware protection layers

Patch Information

HP has released updated UEFI firmware versions to address this vulnerability. Administrators should consult the HP Security Advisory for specific firmware versions and download links for each affected product. The advisory contains detailed information on the minimum firmware versions required to remediate CVE-2021-39297 across all affected HP product lines.

Firmware updates should be applied during scheduled maintenance windows following proper backup procedures. For enterprise deployments, HP provides tools for managed firmware deployment including HP Image Assistant and HP Client Management Solutions.

Workarounds

• Implement strict physical access controls to affected systems to reduce local attack surface
• Enable BIOS/UEFI password protection to prevent unauthorized firmware configuration changes
• Deploy application whitelisting and privilege access management to limit local privilege escalation opportunities
• Utilize network segmentation to isolate systems with vulnerable firmware until patches can be applied

# Example: Check HP BIOS version on Windows using PowerShell
Get-WmiObject -Class Win32_BIOS | Select-Object SMBIOSBIOSVersion, ReleaseDate, Manufacturer

# Example: Check BIOS version on Linux
sudo dmidecode -t bios | grep -E "Version|Release Date|Vendor"

# Verify firmware update completion by comparing against HP advisory versions
# Consult HP Support document ish_5661066-5661090-16 for required versions