FortiswitchOperating system · Fortinet
CVE-2021-26111
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 missing release of memory after effective lifetime vulnerability in FortiSwitch 6.4.0 to 6.4.6, 6.2.0 to 6.2.6, 6.0.0 to 6.0.6, 3.6.11 and below may allow an attacker on an adjacent network to exhaust available memory by sending specifically crafted LLDP/CDP/EDP packets to the device.
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 confidenceA memory leak vulnerability in FortiSwitch firmware allows an attacker on an adjacent network to send specially crafted LLDP, CDP, or EDP packets, causing memory to be allocated but never released, eventually exhausting available memory and potentially leading to denial of service.
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
FortiswitchOperating system
<= 3.6.11>= 6.0.0, <= 6.0.6>= 6.2.0, <= 6.2.6>= 6.4.0, <= 6.4.6CVSS 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
- Adjacent
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:A/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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Determine FortiSwitch firmware versionRun 'get system status' via FortiSwitch CLI or check the dashboard in FortiGate web interface under FortiSwitch managed devicesAffected if The version output is <= 3.6.11, >= 6.0.0 and <= 6.0.6, >= 6.2.0 and <= 6.2.6, or >= 6.4.0 and <= 6.4.6
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Verify LLDP is enabledRun 'get switch lldp status' via FortiSwitch CLI; on FortiGate, check under FortiSwitch > FortiSwitch Ports > LLDP settingsAffected if LLDP is enabled and the firmware version is in the affected ranges
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Verify CDP is enabledRun 'get switch cdp status' via FortiSwitch CLI or check FortiGate FortiSwitch port settings for CDP forwardingAffected if CDP is enabled and the firmware version is in the affected ranges
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Verify EDP is enabledRun 'get switch edp status' via FortiSwitch CLI or check FortiGate FortiSwitch port settings for EDP forwardingAffected if EDP is enabled and the firmware version is in the affected ranges
Your FortiSwitch is affected if it runs any firmware version listed in the affected ranges AND has at least one of LLDP, CDP, or EDP protocols enabled, allowing adjacent network attackers to trigger the memory leak.
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.
From vendor dataUpgrade FortiSwitch firmware to versions 6.4.7, 6.2.7, 6.0.7, or 3.6.12 and above to patch the memory management flaw. Consider network segmentation to limit adjacent network attack surface.
Fix this in Fortiswitch
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 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 $3,040.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-26111 — 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-2021-26111 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
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