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Fortiextender FirmwareOperating system · Fortinet

CVE-2021-41016

HIGH · 8.8 CVSS v3.1 Published 2022-02-02
Fix available
A fix is available. Upgrade to 4.1.8 / 4.2.4 or later.
See remediation →
94/100
Remediation priority · Urgent
Remotely reachable 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 improper neutralization of special elements used in a command ('command injection') in Fortinet FortiExtender version 7.0.1 and below, 4.2.3 and below, 4.1.7 and below allows an authenticated attacker to execute privileged shell commands via CLI commands including special characters

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

Command injection vulnerability in FortiExtender CLI allows authenticated attackers to execute privileged shell commands through specially crafted CLI commands containing special characters that are not properly sanitized.

MitigationApply vendor-supplied patches by upgrading FortiExtender to version 7.0.2 or later, 4.2.4 or later, or 4.1.8 or later. Limit CLI access to trusted administrators only.

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
Fortiextender FirmwareOperating system
Affected:>= 4.1.1, < 4.1.8>= 4.2.0, < 4.2.4>= 7.0.0, < 7.0.2

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

CVSS:3.1/AV:N/AC:L/PR:L/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. Confirm FortiExtender product is in use
    Access the CLI and run `get system status` or check the web UI dashboard to identify the device model
    Affected if The device is not a Fortinet FortiExtender
  2. Identify the firmware version
    Run `get system status` in the FortiExtender CLI or check the firmware version displayed in the web UI under System > Firmware
    Affected if The installed firmware version falls within these ranges: 4.1.1 to 4.1.7, 4.2.0 to 4.2.3, or 7.0.0 to 7.0.1
  3. Verify CLI interface is accessible
    Confirm that SSH or console access to the FortiExtender CLI is enabled and reachable on the network
    Affected if CLI access is exposed to untrusted networks or the internet without proper network restrictions
  4. Check for unauthorized CLI access
    Review FortiExtender CLI logs or system logs for commands containing unusual characters such as semicolons, pipes, backticks, or $() constructs that may indicate injection attempts
    Affected if Any suspicious CLI commands with special shell characters are found in logs

You are affected if you are running FortiExtender firmware version 4.1.1-4.1.7, 4.2.0-4.2.3, or 7.0.0-7.0.1 with CLI access available to authenticated users.

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 4.1.8 / 4.2.4 / 7.0.2 or later
Fixed in 4.1.84.2.47.0.2
Interim mitigation

Apply vendor-supplied patches by upgrading FortiExtender to version 7.0.2 or later, 4.2.4 or later, or 4.1.8 or later. Limit CLI access to trusted administrators only.

Recommended fix High confidence

FortiExtender 4.1.8+, 4.2.4+, or 7.0.2+ depending on current branch

  1. 1. Identify the current FortiExtender firmware version by accessing the FortiExtender CLI or web interface
  2. 2. Determine which version branch (4.1.x, 4.2.x, or 7.0.x) is currently in use
  3. 3. For 4.1.x branch users: upgrade to FortiExtender firmware version 4.1.8 or later
  4. 4. For 4.2.x branch users: upgrade to FortiExtender firmware version 4.2.4 or later
  5. 5. For 7.0.x branch users: upgrade to FortiExtender firmware version 7.0.2 or later
  6. 6. Download the appropriate firmware from Fortinet's support portal (support.fortinet.com)
  7. 7. Upload the firmware upgrade via the FortiExtender web UI under System > Firmware or via CLI using 'execute firmware upgrade'
  8. 8. After upgrade, verify the new firmware version is installed and test that the device operates normally
Caveat Review FortiExtender release notes for your target version to check for configuration or feature changes between versions; firmware upgrades may require brief downtime

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

Fix this in Fortiextender Firmware Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
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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-2021-41016 in production — separate from our analysis above.

No notes yet

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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
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data