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CVE Record

CVE-2021-26111: A missing release of memory after effective lifetime vulnerability in FortiSwitch 6.4.0 to 6.4.6, 6.2.0 to...

A 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.

MediumCVSS 6.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

Affected FortiSwitch devices can run out of memory when crafted link-discovery traffic reaches them from an adjacent network. The main business impact is switch instability or outage, not data theft. Risk is lower than internet-reachable flaws, but material for shared, untrusted, or poorly segmented local networks.

Executive priority

Treat as a moderate availability risk. Prioritize remediation where affected switches support business-critical connectivity or face untrusted adjacent networks. This is not described as a confidentiality breach, but outages in switching infrastructure can have broad operational consequences.

Technical view

CVE-2021-26111 is a memory-release flaw in Fortinet FortiSwitch handling of LLDP, CDP, or EDP packets. A network-adjacent unauthenticated attacker may exhaust device memory, causing high availability impact. The CVSS vector is AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H with score 6.5.

Likely exposure

Exposure is limited to FortiSwitch 6.4.0-6.4.6, 6.2.0-6.2.6, 6.0.0-6.0.6, and 3.6.11 or below. The attacker must be on an adjacent network path capable of reaching discovery-protocol handling.

Exploitation context

The bundle does not show CISA KEV listing or cited evidence of active exploitation. Exploitation requires adjacent-network access and crafted LLDP, CDP, or EDP traffic. Impact is availability disruption through memory exhaustion.

Researcher notes

The source data names affected versions, adjacent attack vector, no required privileges, and high availability impact. It does not provide exploit evidence, detailed vulnerable code paths, or explicit fixed versions in the supplied bundle, so remediation should be tied directly to Fortinet guidance.

Mitigation direction

  • Identify FortiSwitch devices and map firmware versions against the affected ranges.
  • Review Fortinet advisory FG-IR-21-026 for vendor-approved fixed releases or mitigations.
  • Prioritize upgrades for switches on shared, guest, campus, or provider-adjacent networks.
  • Restrict untrusted Layer 2 adjacency where operationally possible.
  • Monitor FortiSwitch memory, restarts, and interface-adjacent anomalies.

Validation and detection

  • Inventory FortiSwitch firmware versions and confirm whether listed affected trains are present.
  • Confirm whether LLDP, CDP, or EDP exposure exists on untrusted adjacent segments.
  • Check device telemetry for abnormal memory growth or unexpected switch instability.
  • Verify remediation status against Fortinet’s advisory, not inferred version assumptions.
Prepared
Confidence
medium
Sources
3

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2021-26111 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
6.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
2Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
6.5CVSS 3.1MediumCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H2.83.6Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

6.5Medium
CVSS 3.1 vector shape for CVE-2021-26111Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
FortinetFortinet FortiSwitchFortiSwitch 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 belowListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.