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Zynq 7000s FirmwareOperating system · Xilinx

CVE-2021-27208

MEDIUM · 6.8 CVSS v3.1 Published 2021-03-15
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
73/100
Remediation priority · Elevated
No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
When booting a Zync-7000 SOC device from nand flash memory, the nand driver in the ROM does not validate the inputs when reading in any parameters in the nand’s parameter page. IF a field read in from the parameter page is too large, this causes a buffer overflow that could lead to arbitrary code execution. Physical access and modification of the board assembly on which the Zynq-7000 SoC device mounted is needed to replace the original NAND flash memory with a NAND flash emulation device for this attack to be successful.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Buffer overflow vulnerability in the Zynq-7000 SoC ROM NAND driver where parameters read from the NAND flash parameter page are not validated for size, allowing an oversized field to overflow and enable arbitrary code execution during boot.

MitigationRestrict physical access to devices; if NAND boot is not required, disable NAND boot mode and use alternative boot sources; implement secure boot if available to validate firmware integrity.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Zynq 7000s FirmwareOperating system
Affected:all versions
Zynq 7000 FirmwareOperating system
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Physical
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Zynq-7000 hardware platform
    Review device documentation, schematics, or boot configuration settings to confirm the SoC is either Xilinx Zynq-7000 or Zynq-7000s. Check the device tree or hardware identification registers if accessible.
    Affected if The device is not a Zynq-7000 or Zynq-7000s series SoC, then this CVE does not apply.
  2. Verify NAND boot mode is enabled
    Inspect the boot mode settings or boot configuration registers (e.g., BSPI registers, boot mode pins) to determine if the device is configured to boot from NAND flash. Check the primary boot device setting in the boot header or boot ROM configuration.
    Affected if The device uses NAND flash as the boot source, making the NAND driver ROM code active during early boot.
  3. Inspect NAND parameter page configuration
    Read the NAND flash parameter page (ONFI parameter page) stored on the NAND device. This is typically located at a fixed offset in the NAND flash (often block 0, page 0 or similar). Use NAND flash reader tools or check the boot image for embedded NAND parameters.
    Affected if The NAND parameter page contains fields (such as model number, manufacturer ID, or other variable-length fields) that could exceed the expected buffer size in the ROM driver.
  4. Check for custom or oversized NAND parameters
    Examine the NAND parameter page data for unusually long ASCII strings or fields that extend beyond their defined boundaries in the ONFI specification. Compare field lengths against ROM driver buffer expectations.
    Affected if Any field in the NAND parameter page is larger than what the ROM NAND driver expects, indicating potential buffer overflow condition.

If the device is a Zynq-7000 or Zynq-7000s using NAND flash boot mode with a NAND parameter page containing oversized fields, the device is vulnerable to arbitrary code execution during boot.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Restrict physical access to devices; if NAND boot is not required, disable NAND boot mode and use alternative boot sources; implement secure boot if available to validate firmware integrity.

Fix this in Zynq 7000s Firmware Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
30.0 hours of engineering $5,280
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-27208 in production — separate from our analysis above.

No notes yet

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What this is

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What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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