CVE-2021-27208Public exploit

Physical code execution via unchecked NAND parameters

Published Mar 15, 2021 · Updated Aug 3, 2024

Buffer overflow in the Zynq-7000 SoC boot ROM NAND driver allows physically proximate attackers to execute arbitrary code during NAND boot. XNandPs_ReadSpareBytes trusts SpareBytesPerPage from the ONFI parameter page and copies that many bytes into a 0x200-byte stack buffer in XNandPs_SearchBbt. Exploitation requires physical board modification to replace the original NAND with an emulator that supplies crafted parameters, enabling boot-ROM control, JTAG unlocking, or a crash.

CVSS severity6.8
Medium
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer overflow in the Zynq-7000 SoC boot ROM NAND driver allows physically proximate attackers to execute arbitrary code during NAND boot. XNandPs_ReadSpareBytes trusts SpareBytesPerPage from the ONFI parameter page and copies that many bytes into a 0x200-byte stack buffer in XNandPs_SearchBbt. Exploitation requires physical board modification to replace the original NAND with an emulator that supplies crafted parameters, enabling boot-ROM control, JTAG unlocking, or a crash.

The record

CVE
CVE-2021-27208
Published
Mar 15, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-120, T1200
Attack vector
physical
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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 vectorphysical
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.6NIST NVDAV:L/AC:L/Au:N/C:P/I:P/A:P
6.8NIST NVDCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/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 exploitPublished

Weakness, pattern, technique

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
T1200Hardware Additions

Public exploit references

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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