CVE-2021-39300

Privileged firmware code execution via oversized NVRAM variable

Published Feb 16, 2022 · Updated Aug 4, 2024

Stack-based buffer overflow in HP PC UEFI firmware allows local users to execute arbitrary code in a DXE driver. The driver calls GetVariable twice for the CoolControlData NVRAM variable and lets a value longer than eight bytes overflow a stack buffer. Administrative access is required; successful exploitation can persist across operating-system boots, alter NVRAM or EFI runtime services, and bypass OS security controls.

CVSS severity7.5
High
EPSS probability0.42%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in HP PC UEFI firmware allows local users to execute arbitrary code in a DXE driver. The driver calls GetVariable twice for the CoolControlData NVRAM variable and lets a value longer than eight bytes overflow a stack buffer. Administrative access is required; successful exploitation can persist across operating-system boots, alter NVRAM or EFI runtime services, and bypass OS security controls.

The record

CVE
CVE-2021-39300
Published
Feb 16, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-121, T1068, T1542.001
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Feb 16, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5HP Inc.CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-121Stack-based Buffer Overflow
T1068Exploitation for Privilege Escalation
T1542.001System Firmware

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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