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Z StackApplication · Ti

CVE-2020-27890

HIGH · 8.2 CVSS v3.1 Published 2020-10-27
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
91/100
Remediation priority · Urgent
Remotely reachable 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
The Zigbee protocol implementation on Texas Instruments CC2538 devices with Z-Stack 3.0.1 does not properly process a ZCL Write Attributes No Response message. It crashes in zclParseInWriteCmd() and does not update the specific attribute's value.

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 · moderate confidence

The Zigbee Z-Stack 3.0.1 on Texas Instruments CC2538 devices contains a vulnerability in the zclParseInWriteCmd() function. When processing a specially crafted ZCL Write Attributes No Response message, the device crashes (denial of service) and fails to update the targeted attribute value. This is a parsing logic flaw in the Zigbee cluster library handling write attribute commands.

MitigationUpdate to a patched Z-Stack version from Texas Instruments, or if unavailable, implement network-level controls to filter unauthorized Zigbee traffic targeting ZCL write attribute commands.

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
Z StackApplication
Affected:= 3.0.1

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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 the hardware platform
    Check if the Zigbee device is based on the Texas Instruments CC2538 system-on-chip. This may be documented in device specifications, firmware build information, or by inspecting the hardware itself for TI CC2538 markings.
    Affected if The device uses TI CC2538 hardware - only this platform is affected by this CVE.
  2. Determine the Z-Stack firmware version
    Query the device firmware metadata or check the Z-Stack version string. On TI CC2538 devices, this can often be retrieved via debug interfaces, firmware metadata, or by querying the device's Z-Stack version attribute if exposed through ZCL device information cluster.
    Affected if The installed Z-Stack version is exactly 3.0.1 - this is the only version listed as affected.
  3. Verify ZCL write attribute processing is enabled
    Confirm that the device has an active Zigbee endpoint implementing ZCL (Zigbee Cluster Library) with write attribute functionality. This is standard on most Zigbee devices but can be verified by checking the device's cluster configuration or monitoring Zigbee traffic for Write Attributes or Write Attributes No Response commands.
    Affected if The device processes incoming ZCL Write Attributes No Response commands - this is the attack vector for triggering the vulnerability.
  4. Monitor for attribute update failures
    Attempt to send a legitimate ZCL Write Attributes No Response command to the device and verify whether the targeted attribute value is updated correctly. Alternatively, review device logs or network captures for evidence of failed attribute writes or unexpected device behavior.
    Affected if The Write Attributes No Response command fails to update the targeted attribute value while other write commands succeed - this indicates the parsing flaw may be present.
  5. Check for device crashes or resets
    Monitor the device for unexpected resets, crashes, or denial of service conditions, particularly after processing Zigbee traffic containing ZCL write attribute commands. Review device logs, uptime statistics, or network monitoring for crash indicators.
    Affected if The device crashes or becomes unresponsive specifically when processing ZCL Write Attributes No Response messages - this confirms the vulnerability is present and triggerable.

A device is affected if it uses TI CC2538 hardware running Z-Stack version 3.0.1 and processes ZCL Write Attributes No Response commands, as the parsing flaw causes attribute update failures and potential device crashes.

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

Update to a patched Z-Stack version from Texas Instruments, or if unavailable, implement network-level controls to filter unauthorized Zigbee traffic targeting ZCL write attribute commands.

Fix this in Z Stack Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA3.0 h
21.0 hours of engineering $3,680
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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-2020-27890 in production — separate from our analysis above.

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What belongs here
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  • Version or environment caveats, and links to real fixes
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