dbcve.org
FortiauthenticatorApplication · Fortinet

CVE-2021-26116

HIGH · 8.8 CVSS v3.1 Published 2022-04-06
Fix available
A fix is available. Upgrade to 6.3.1 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
An improper neutralization of special elements used in an OS command vulnerability in the command line interpreter of FortiAuthenticator before 6.3.1 may allow an authenticated attacker to execute unauthorized commands via specifically crafted arguments to existing 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

FortiAuthenticator versions before 6.3.1 contain an OS command injection vulnerability in the command line interpreter. An authenticated attacker can execute arbitrary OS commands by providing specially crafted arguments to existing CLI commands, due to improper neutralization of special elements.

MitigationUpgrade FortiAuthenticator to version 6.3.1 or later. Until then, limit CLI access to trusted administrators only and monitor for suspicious command execution.

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
FortiauthenticatorApplication
Affected:>= 5.0.0, < 6.3.1

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
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. Identify FortiAuthenticator version
    Log into the FortiAuthenticator web UI or CLI and retrieve the current firmware version. In the web UI this is typically shown in the Dashboard or System > Settings. In CLI, use the 'get system status' command.
    Affected if The installed version is 5.0.0 or higher but lower than 6.3.1
  2. Confirm CLI access is enabled
    Check that the command line interface service is enabled and accessible. This is typically configured under System > Settings or in the CLI under 'config system interface' to verify SSH or console access is permitted.
    Affected if CLI access (SSH or console) is enabled and the version is in the affected range
  3. Verify network exposure of CLI service
    Review the network interface bindings for the CLI service (SSH on port 22 by default). Determine if it is bound to a trusted internal interface or exposed to untrusted networks.
    Affected if The CLI service is reachable from untrusted or external networks and the version is in the affected range
  4. Review CLI command logs for anomalies
    Examine FortiAuthenticator logs for suspicious or unexpected CLI commands, particularly those containing unusual arguments, shell metacharacters, or commands that deviate from normal administrative operations.
    Affected if Suspicious commands are found in logs and the version is in the affected range

You are affected if FortiAuthenticator is running version 5.0.0 or higher but lower than 6.3.1 and the CLI interface is accessible to the attacker.

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 6.3.1 or later
Fixed in 6.3.1
Interim mitigation

Upgrade FortiAuthenticator to version 6.3.1 or later. Until then, limit CLI access to trusted administrators only and monitor for suspicious command execution.

Recommended fix High confidence

FortiAuthenticator 6.3.1 or later

  1. 1. Back up the current FortiAuthenticator configuration before upgrading.
  2. 2. Obtain FortiAuthenticator version 6.3.1 or later from the Fortinet support portal (fortinet.com).
  3. 3. Upload the firmware image through the FortiAuthenticator web GUI under System > Firmware or via CLI using the execute firmware upgrade command.
  4. 4. Follow Fortinet's standard firmware upgrade procedure, ensuring stable power during the process.
  5. 5. After reboot, verify the upgrade was successful by checking the firmware version in the GUI (System > Dashboard > Status) or via CLI: get system status.
  6. 6. Confirm the version is 6.3.1 or higher and that the OS command injection vulnerability is remediated.

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

Fix this in Fortiauthenticator Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,720
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,752.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-26116 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2021-26116 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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