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FortiwebApplication · Fortinet

CVE-2020-29016

CRITICAL · 9.8 CVSS v3.1 Published 2021-01-14
Fix available
A fix is available. Upgrade to 6.2.4 or later.
See remediation →
100/100
Remediation priority · Urgent
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
A stack-based buffer overflow vulnerability in FortiWeb 6.3.0 through 6.3.5 and version before 6.2.4 may allow an unauthenticated, remote attacker to overwrite the content of the stack and potentially execute arbitrary code by sending a crafted request with a large certname.

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

A stack-based buffer overflow exists in FortiWeb's handling of the 'certname' parameter. When processing a crafted HTTP request containing an oversized certificate name, the vulnerable code copies the user-controlled input into a fixed-size stack buffer without proper bounds checking, allowing an unauthenticated attacker to overwrite stack memory and potentially execute arbitrary code.

MitigationUpgrade FortiWeb to version 6.2.4 or later, or 6.3.6 or later. As a critical CVSS 9.8 vulnerability with remote unauthenticated code execution potential, this should be prioritized for immediate remediation.

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
FortiwebApplication
Affected:< 6.2.4>= 6.3.0, <= 6.3.5

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
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/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. Check FortiWeb firmware version via CLI
    Run the command: `get system status` or `fnsysctl get system status` to retrieve the firmware version.
    Affected if The version is below 6.2.4, or is 6.3.0 through 6.3.5 inclusive.
  2. Check FortiWeb version via web UI
    Log into the FortiWeb web interface and navigate to System > Status to view the firmware version displayed on the dashboard.
    Affected if The version displayed is below 6.2.4, or falls between 6.3.0 and 6.3.5 inclusive.
  3. Verify SSL certificate configuration is in use
    Check if the FortiWeb appliance is configured with SSL/TLS certificates for protected web servers. In the web UI, navigate to Server Objects > SSL > Certificates to see if any certificates are defined.
    Affected if The 'certname' parameter vulnerability applies when SSL certificate configuration exists and the device accepts HTTP requests for certificate name handling.

A FortiWeb device is affected if it is running firmware version 6.2.3 or earlier, or version 6.3.0 through 6.3.5, and has SSL certificate configuration enabled.

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 6.2.4 or later
Fixed in 6.2.4
Interim mitigation

Upgrade FortiWeb to version 6.2.4 or later, or 6.3.6 or later. As a critical CVSS 9.8 vulnerability with remote unauthenticated code execution potential, this should be prioritized for immediate remediation.

Recommended fix High confidence

FortiWeb 6.2.4 or later (6.2.x branch); FortiWeb 6.3.6 or later (6.3.x branch); or latest stable 6.4.x/7.x

  1. 1. Identify the current FortiWeb version by running 'get system status' or checking the FortiWeb GUI dashboard.
  2. 2. If running version < 6.2.4, upgrade to FortiWeb 6.2.4 or later.
  3. 3. If running version 6.3.0 through 6.3.5, upgrade to FortiWeb 6.3.6 or later, or preferably the latest stable version (6.4.x or 7.x).
  4. 4. Download the upgrade image from Fortinet Customer Support portal (https://support.fortinet.com/).
  5. 5. Back up the FortiWeb configuration before upgrading.
  6. 6. Upload the new firmware via FortiWeb GUI (System > Firmware) or CLI ('execute firmware upgrade').
  7. 7. After upgrade, verify the new version is installed and confirm the vulnerability is resolved.
Caveat Review FortiWeb release notes for migration considerations between major versions; some configuration adjustments may be needed when upgrading across major branches

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

Fix this in Fortiweb Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,840
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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-2020-29016 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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  • No spam, self-promotion, credentials, or personal data