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CVE Record

CVE-2021-24018: A buffer underwrite vulnerability in the firmware verification routine of FortiOS before 7.0.1 may allow an...

A buffer underwrite vulnerability in the firmware verification routine of FortiOS before 7.0.1 may allow an attacker located in the adjacent network to potentially execute arbitrary code via a specifically crafted firmware image.

MediumCVSS 4.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

FortiOS versions before 7.0.1 contain a firmware verification flaw. An attacker already near the device network and holding high privileges could use a crafted firmware image to potentially run arbitrary code. This is not described as remotely exploitable from the internet.

Executive priority

Treat this as a controlled remediation item, not an emergency internet-wide incident, unless vulnerable FortiOS management paths are exposed to untrusted networks.

Technical view

CVE-2021-24018 is a buffer underwrite in the FortiOS firmware verification routine. The CVSS vector is AV:A/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:L, with CVSS 3.1 score 4.3. Affected product is Fortinet FortiOS before 7.0.1.

Likely exposure

Exposure is limited to FortiOS deployments running versions before 7.0.1, especially where firmware update or administrative paths are reachable from adjacent networks.

Exploitation context

The source bundle does not show CISA KEV listing or active exploitation evidence. Requirements are meaningful: adjacent-network access and high privileges are needed before the crafted firmware image path matters.

Researcher notes

No CWE is listed in the supplied sources. The strongest technical signals are buffer underwrite, firmware verification routine, adjacent access, high privileges, and low confidentiality, integrity, and availability impact.

Mitigation direction

  • Confirm Fortinet guidance in advisory FG-IR-21-046.
  • Upgrade affected FortiOS systems to 7.0.1 or a later supported fixed release.
  • Restrict administrative and firmware update access to trusted management networks.
  • Limit privileged FortiOS accounts to named administrators with strong authentication.
  • Monitor Fortinet advisories for any revised affected-version or remediation details.

Validation and detection

  • Inventory all FortiOS versions and flag systems before 7.0.1.
  • Confirm management interfaces are not reachable from untrusted adjacent networks.
  • Review privileged account access to firmware update workflows.
  • Check change records for completion of FortiOS upgrade remediation.
  • Track whether Fortinet advisory FG-IR-21-046 changes severity, scope, or fixes.
Prepared
Confidence
high
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

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

description · low confidence lookup

Execution behavior lookup

The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2021-24018 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Medium
CVSS
4.3 (3.1)
Known Exploited
No
Published

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

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
4.3CVSS 3.1MediumCVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:L/E:X/RL:U/RC:C0.93.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

4.3Medium
CVSS 3.1 vector shape for CVE-2021-24018Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

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 FortiOSFortiOS before 7.0.1Listed
Weakness

CWE details

No CWE listed

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