dbcve.org
FortiosOperating system · Fortinet

CVE-2021-36169

MEDIUM · 6.0 CVSS v3.1 Published 2021-12-13
Fix available
A fix is available. Upgrade to 6.2.10 / 6.4.7 or later.
See remediation →
62/100
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 Hidden Functionality in Fortinet FortiOS 7.x before 7.0.1, FortiOS 6.4.x before 6.4.7 allows attacker to Execute unauthorized code or commands via specific hex read/write operations.

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

A hidden functionality in Fortinet FortiOS 7.x before 7.0.1 and 6.4.x before 6.4.7 allows remote attackers to execute unauthorized code or commands via specific hex read/write operations. This appears to be an undocumented backdoor or debug feature in the firmware that accepts hex-encoded input to perform privileged operations.

MitigationUpgrade FortiOS to version 7.0.1 or higher (for 7.x branch) or 6.4.7 or higher (for 6.4.x branch) to remove the unauthorized functionality. Apply the upgrade during a scheduled maintenance window with configuration backups.

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
FortiosOperating system
Affected:>= 5.6.0, <= 5.6.14>= 6.0.0, <= 6.0.14>= 6.2.0, < 6.2.10>= 6.4.0, < 6.4.7= 7.0.0

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
None

CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/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. Check FortiOS version via CLI
    Log into the FortiGate CLI and run `get system status` or `diagnose sys status` to retrieve the firmware version
    Affected if The displayed firmware version falls within any of these ranges: 5.6.0-5.6.14, 6.0.0-6.0.14, 6.2.0-6.2.9, 6.4.0-6.4.6, or 7.0.0 exactly
  2. Verify no patches have been applied
    In the CLI, run `diagnose system patch info` or check the release notes for any hotpatch status
    Affected if No patch or hotfix addressing CVE-2021-36169 has been applied to the system
  3. Inspect for unauthorized listening services
    Run `diagnose netstat -lp` or `show system interface` to list all listening services and network listeners on the device
    Affected if Unexpected services are listening, particularly on unusual ports that may be related to the hex-encoded backdoor functionality

A system is affected if it runs FortiOS version 5.6.0-5.6.14, 6.0.0-6.0.14, 6.2.0-6.2.9, 6.4.0-6.4.6, or exactly 7.0.0 without the corresponding security patch applied.

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 6.2.10 / 6.4.7 or later
Fixed in 6.2.106.4.7
Interim mitigation

Upgrade FortiOS to version 7.0.1 or higher (for 7.x branch) or 6.4.7 or higher (for 6.4.x branch) to remove the unauthorized functionality. Apply the upgrade during a scheduled maintenance window with configuration backups.

Recommended fix High confidence

FortiOS 6.4.7 or later; FortiOS 7.0.1 or later (for 5.6.x/6.0.x/6.2.x migrate to 6.4.7+/7.0.1+)

  1. 1. Identify the current FortiOS version by running 'get system status' or checking the FortiOS GUI dashboard
  2. 2. Confirm the version falls within one of the affected ranges: 5.6.0-5.6.14, 6.0.0-6.0.14, 6.2.0-6.2.9, or 6.4.0-6.4.6
  3. 3. Backup the current FortiOS configuration using 'execute backup config tftp/ftp/scp' or via GUI
  4. 4. Review Fortinet release notes for the target fixed version to understand any migration considerations
  5. 5. For FortiOS 6.4.x: Upgrade to version 6.4.7 or later
  6. 6. For FortiOS 7.x: Upgrade to version 7.0.1 or later
  7. 7. For FortiOS 5.6.x and 6.0.x: Upgrade to a version beyond the listed affected ranges (6.2.10+, 6.4.7+, or 7.0.1+)
  8. 8. After upgrade, verify the system is operational and run 'get system status' to confirm the new version
Caveat Review Fortinet release notes for the target version - some upgrades may require sequential version stepping or have compatibility considerations with FortiGate models and installed features

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

Fix this in Fortios 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-2021-36169 — 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-2021-36169 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