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Unifi Meshing Access Point FirmwareOperating system · Ui

CVE-2020-27888

HIGH · 7.5 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 →
84/100
Remediation priority · High
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
An issue was discovered on Ubiquiti UniFi Meshing Access Point UAP-AC-M 4.3.21.11325 and UniFi Controller 6.0.28 devices. Cached credentials are not erased from an access point returning wirelessly from a disconnected state. This may provide unintended network access.

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

On Ubiquiti UniFi mesh access points (UAP-AC-M) running firmware 4.3.21.11325 and UniFi Controller 6.0.28, authentication credentials cached locally on the access point are not properly cleared when the AP transitions from a disconnected state back to a meshed/reconnected state. This allows an AP that rejoins the mesh network after a period of disconnection to retain previous authentication materials, potentially enabling unauthorized network access.

MitigationUpgrade UniFi Controller and mesh AP firmware to vendor-patched versions that properly clear cached credentials upon mesh reconnection; consider force-reprovisioning or factory-resetting access points that have experienced disconnected states to ensure credential cache is cleared.

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
Unifi Meshing Access Point FirmwareOperating system
Affected:= 4.3.21.11325
Unifi Controller FirmwareOperating system
Affected:= 6.0.28

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
High
Integrity
None
Availability
None

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

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 mesh-capable access point model
    Log into UniFi Controller and navigate to Devices section. Check the device model column for UAP-AC-M or other mesh-capable AP models (UAP-AC-Mesh, UAP-nanoHD, etc.). Note: Only mesh-capable models are affected by this vulnerability.
    Affected if Device model is not a Ubiquiti mesh-capable access point (UAP-AC-M or similar)
  2. Check AP firmware version
    In UniFi Controller, select the mesh AP device and view the firmware version displayed in the device details panel. Alternatively, use SSH to connect to the AP and run 'info' command to display firmware version.
    Affected if Firmware version is NOT 4.3.21.11325 (the specific affected version)
  3. Check UniFi Controller version
    In UniFi Controller web interface, click on the gear icon (settings) and look for the controller version in the bottom-left corner, or check System -> Controller for version information.
    Affected if Controller version is NOT 6.0.28 (the specific affected version)
  4. Verify AP disconnection/reconnection history
    In UniFi Controller, select the mesh AP and check the Events/Logs tab for disconnection and reconnection events. Look for status changes from 'Disconnected' to 'Connected' indicating the AP has transitioned from a disconnected state back to the mesh network.
    Affected if AP has NOT experienced a disconnection and subsequent reconnection event (the vulnerable state transition has not occurred)

Affected if the AP is a mesh-capable model (UAP-AC-M) running firmware 4.3.21.11325, managed by UniFi Controller 6.0.28, and has transitioned from a disconnected state back to a connected mesh state.

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

Upgrade UniFi Controller and mesh AP firmware to vendor-patched versions that properly clear cached credentials upon mesh reconnection; consider force-reprovisioning or factory-resetting access points that have experienced disconnected states to ensure credential cache is cleared.

Fix this in Unifi Meshing Access Point Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2020-27888 in production — separate from our analysis above.

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What this is

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