CVE-2021-39297

8.8 HIGH

📋 TL;DR

This UEFI firmware vulnerability in certain HP PC products allows attackers with physical or administrative access to execute arbitrary code at the firmware level. This affects specific HP PC models with vulnerable BIOS versions, potentially compromising the entire system before the operating system loads.

💻 Affected Systems

Products:
  • HP PC products (specific models listed in HP advisory)
Versions: Multiple BIOS versions for affected HP PC models
Operating Systems: All operating systems running on affected hardware
Default Config Vulnerable: ⚠️ Yes
Notes: Affects specific HP PC models only; requires checking HP advisory for exact model/BIOS combinations.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete system compromise with persistent firmware-level malware that survives OS reinstallation and disk replacement, enabling data theft, ransomware deployment, or system bricking.

🟠

Likely Case

Privilege escalation from administrative user to firmware-level control, allowing installation of persistent backdoors or disabling security features.

🟢

If Mitigated

Limited impact if physical access controls prevent unauthorized BIOS access and administrative privileges are tightly controlled.

🌐 Internet-Facing: LOW - Requires physical or administrative access, not directly exploitable over network.
🏢 Internal Only: HIGH - Malicious insiders or compromised admin accounts could exploit this for persistent access.

🎯 Exploit Status

Public PoC: ✅ No
Weaponized: UNKNOWN
Unauthenticated Exploit: ✅ No
Complexity: MEDIUM

Requires administrative access or physical access to BIOS settings. No public exploit code available.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: BIOS updates specific to each affected HP PC model

Vendor Advisory: https://support.hp.com/us-en/document/ish_5661066-5661090-16

Restart Required: Yes

Instructions:

1. Identify exact HP PC model. 2. Visit HP support site. 3. Download latest BIOS update for your model. 4. Run BIOS update utility. 5. Restart system as prompted.

🔧 Temporary Workarounds

Restrict physical access

all

Prevent unauthorized physical access to systems to block BIOS manipulation.

Enable BIOS password

all

Set strong BIOS administrator password to prevent unauthorized BIOS changes.

🧯 If You Can't Patch

  • Isolate affected systems on separate network segments
  • Implement strict administrative access controls and monitoring

🔍 How to Verify

Check if Vulnerable:

Check HP advisory for affected models and compare with your system's model and BIOS version (check in BIOS setup or using 'wmic bios get smbiosbiosversion' on Windows).

Check Version:

Windows: wmic bios get smbiosbiosversion | Linux: sudo dmidecode -s bios-version

Verify Fix Applied:

Verify BIOS version after update matches patched version in HP advisory.

📡 Detection & Monitoring

Log Indicators:

  • Unexpected BIOS update attempts
  • BIOS configuration changes in system logs
  • Failed BIOS password attempts

Network Indicators:

  • Unusual outbound connections from systems with vulnerable BIOS

SIEM Query:

Search for BIOS-related events or unauthorized firmware update attempts in system logs.

🔗 References

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