CVE-2020-25647

Secure Boot bypass via unchecked USB descriptors

Published Mar 3, 2021 · Updated Aug 4, 2024

Out-of-bounds write in GNU GRUB before 2.06 allows physically proximate attackers to execute arbitrary code via crafted USB descriptors. grub_usb_device_initialize() trusts descriptor-provided lengths while populating USB structures without sufficient bounds checks, corrupting memory outside the intended buffer. Exploitation requires a malicious USB device during boot and can bypass Secure Boot; builds without the GRUB USB module are not exposed.

CVSS severity7.6
High
EPSS probability0.79%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in GNU GRUB before 2.06 allows physically proximate attackers to execute arbitrary code via crafted USB descriptors. grub_usb_device_initialize() trusts descriptor-provided lengths while populating USB structures without sufficient bounds checks, corrupting memory outside the intended buffer. Exploitation requires a malicious USB device during boot and can bypass Secure Boot; builds without the GRUB USB module are not exposed.

The record

CVE
CVE-2020-25647
Published
Mar 3, 2021
Updated
Aug 4, 2024
Vendor
The GnuPG Project
Product
GNU GRUB
Classifications
CWE-787, T1200
Attack vector
physical
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 3, 2021CVE 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=grub 2.06

What conditions does exploitation require?

Attack vectorphysical
Required privilegesunauthenticated

What is affected?

The GnuPG Project · GNU GRUBversion=grub 2.06

Published CVSS scores

7.6NVDCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
7.6SUSECVSS:3.1/AV:P/AC:L/PR:N/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)
Vectorphysical
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1200Hardware Additions

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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