FortiwebApplication · Fortinet
CVE-2021-36187
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 · uneditedA uncontrolled resource consumption in Fortinet FortiWeb version 6.4.0, version 6.3.15 and below, 6.2.5 and below allows attacker to cause a denial of service for webserver daemon via crafted HTTP requests
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 confidenceFortiWeb's webserver daemon suffers from uncontrolled resource consumption when processing specially crafted HTTP requests, leading to denial of service. This is a resource exhaustion or memory leak vulnerability in the HTTP parsing layer.
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
>= 6.2.0, <= 6.2.5>= 6.3.0, <= 6.3.15= 6.4.0CVSS 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
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 checksWork through these to decide whether this CVE applies to you.
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Retrieve FortiWeb firmware versionLog into FortiWeb CLI and run: get system statusAffected if The displayed version falls within 6.2.0-6.2.5, 6.3.0-6.3.15, or equals 6.4.0
-
Confirm HTTP service is enabledVerify the FortiWeb webserver daemon is active by checking HTTP/HTTPS listeners: show system interface | grep -A5 httpAffected if HTTP or HTTPS service is listening (this is the default configuration for FortiWeb)
You are affected if FortiWeb is running version 6.2.0 through 6.2.5, 6.3.0 through 6.3.15, or exactly 6.4.0 and the HTTP webserver service is enabled.
Generated from the published advisory. Verify against your own configuration.
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 · scopedUpgrade FortiWeb to version 6.4.1, 6.3.16, 6.2.6 or later to patch the vulnerability. If immediate patching is not possible, consider rate limiting or restricting HTTP access to trusted sources at upstream devices.
Upgrade to FortiWeb 6.2.6+ (6.2.x branch), 6.3.16+ (6.3.x branch), or 6.4.1+ (6.4.x branch) - choose the latest available version in your current branch
- 1. Identify the current FortiWeb version by navigating to System > Firmware in the FortiWeb GUI or using 'get system status' in CLI
- 2. Based on your current version branch, plan the upgrade: If running 6.2.x, upgrade to 6.2.6 or later; if running 6.3.x, upgrade to 6.3.16 or later; if running 6.4.0, upgrade to 6.4.1 or later
- 3. Download the appropriate firmware from Fortinet's support portal (https://support.fortinet.com)
- 4. Back up the FortiWeb configuration via System > Maintenance > Backup & Restore in GUI or 'execute backup full-config' in CLI
- 5. Upload the new firmware via System > Firmware > Upgrade in GUI or 'execute firmware upgrade' in CLI
- 6. After reboot, verify the upgrade was successful and confirm the new version via 'get system status'
- 7. Test critical FortiWeb functionality including web application firewall policies and traffic processing
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Fortiweb
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,648.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-36187 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-36187 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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