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Meru FirmwareOperating system · Fortinet

CVE-2021-42759

MEDIUM · 6.7 CVSS v3.1 Published 2021-12-09
Fix available
A fix is available. Upgrade to 8.6.2 or later.
See remediation →
69/100
Remediation priority · Elevated
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
A violation of secure design principles in Fortinet Meru AP version 8.6.1 and below, version 8.5.5 and below allows attacker to execute unauthorized code or commands via crafted cli commands.

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

Fortinet Meru AP wireless access points contain an authentication/authorization bypass vulnerability in their CLI interface. Due to a secure design principle violation, unauthenticated attackers can send crafted CLI commands to execute arbitrary code or system commands on affected AP devices running firmware version 8.6.1 or below (or 8.5.5 and below).

MitigationUpgrade Fortinet Meru AP firmware to a version above 8.6.1 (or the latest patched release for the 8.5.x branch). If immediate patching is not feasible, restrict network access to the CLI management interface using ACLs or place management interfaces in an isolated VLAN.

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
Meru FirmwareOperating system
Affected:>= 8.5.0, <= 8.5.5>= 8.6.0, < 8.6.2

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

CVSS:3.1/AV:L/AC:L/PR:H/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. Determine the firmware version of the Fortinet Meru AP
    Access the AP's web interface or CLI and run the command to display system information, typically 'get system info' or 'show version' in the CLI, or check the Status/Dashboard page in the web UI.
    Affected if The displayed firmware version falls within 8.5.0-8.5.5 or 8.6.0-8.6.1.
  2. Verify CLI management interface exposure
    Check the network configuration to determine if the CLI interface (typically accessed via SSH on port 22 or telnet on port 23) is bound to a globally reachable IP address or is exposed to untrusted networks. Review the management interface binding settings in the AP configuration.
    Affected if The CLI management interface is bound to a WAN-facing IP, is accessible from untrusted networks, or has no ACL restricting access.
  3. Confirm SSH or Telnet access is enabled for CLI
    In the AP's web interface, navigate to the management settings or CLI access configuration to verify whether SSH or Telnet services are enabled.
    Affected if SSH or Telnet access to the CLI is enabled and the device is running a vulnerable firmware version.

The device is affected if it runs firmware version 8.5.0 through 8.5.5 or 8.6.0 through 8.6.1 and has its CLI interface (SSH/Telnet) accessible from the network where attackers could send unauthenticated crafted commands.

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.

dbcve · scoped
Upgrade available Upgrade to 8.6.2 or later
Fixed in 8.6.2
Interim mitigation

Upgrade Fortinet Meru AP firmware to a version above 8.6.1 (or the latest patched release for the 8.5.x branch). If immediate patching is not feasible, restrict network access to the CLI management interface using ACLs or place management interfaces in an isolated VLAN.

Recommended fix Moderate confidence

Meru Firmware 8.6.2 or later (or latest stable 8.x release)

  1. Identify the current Meru AP firmware version using the controller management interface or CLI
  2. Download firmware version 8.6.2 or later from the Fortinet support portal
  3. Upload the new firmware to the Meru Wireless Controller
  4. Follow standard firmware upgrade procedures for Meru APs, typically via the controller's web UI or CLI
  5. After upgrade, verify the firmware version and confirm normal operation of wireless services
Caveat Review Fortinet release notes for 8.6.2 for any feature changes or migration considerations before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Meru Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2021-42759 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

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