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CVE Record

CVE-2021-43066: A external control of file name or path in Fortinet FortiClientWindows version 7.0.2 and below, version 6.4...

A external control of file name or path in Fortinet FortiClientWindows version 7.0.2 and below, version 6.4.6 and below, version 6.2.9 and below, version 6.0.10 and below allows attacker to escalate privilege via the MSI installer.

HighCVSS 8.4Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This Fortinet FortiClientWindows flaw lets a low-privileged local attacker raise privileges through the MSI installer path handling. It is not a remote internet exploit, but it matters on managed Windows endpoints because successful abuse can change or disrupt the system with elevated rights.

Executive priority

Treat this as a high-priority endpoint hygiene issue, especially where FortiClient is widely deployed. It is less urgent than a remote perimeter vulnerability, but privilege escalation can turn a foothold into system-level control.

Technical view

CVE-2021-43066 is external control of file name or path in FortiClientWindows. A local attacker with low privileges can escalate privilege via the MSI installer. Affected versions include 7.0.2 and below, 6.4.6 and below, 6.2.9 and below, and 6.0.10 and below.

Likely exposure

Exposure is limited to Windows endpoints running the listed FortiClientWindows versions. Organizations using FortiClient broadly across employee laptops or workstations should assume endpoint inventory, not perimeter scanning, is the primary discovery path.

Exploitation context

The CVSS vector is local, low complexity, low privileges required, and no user interaction. The bundle does not show CISA KEV listing or cited active exploitation. The vector includes high exploit maturity, but that is not the same as confirmed active exploitation.

Researcher notes

The public bundle provides affected versions, CVSS details, and Fortinet advisory reference, but no full remediation text or exploitation proof. Avoid assuming exact fixed versions unless confirmed from Fortinet’s advisory. Validation should focus on installed product version and endpoint deployment state.

Mitigation direction

  • Inventory FortiClientWindows versions across managed and unmanaged Windows endpoints.
  • Review Fortinet advisory FG-IR-21-154 for fixed releases and vendor guidance.
  • Upgrade affected FortiClientWindows installations according to Fortinet guidance.
  • Restrict local software installation and repair workflows until affected endpoints are updated.
  • Prioritize shared workstations and systems used by lower-privileged interactive users.

Validation and detection

  • Confirm installed FortiClientWindows versions against the affected version ranges.
  • Check endpoint management records for upgrade completion and drift.
  • Review local endpoint logs for unusual installer or repair activity.
  • Verify Fortinet advisory guidance has been applied to all relevant deployment channels.
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.

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CVE-2021-43066 mapping review

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

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.4 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H/E:H/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
8.4CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H/E:H/RL:U/RC:C25.8Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

8.4High
CVSS 3.1 vector shape for CVE-2021-43066Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H/E:H/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 FortiClientWindowsFortiClientWindows 7.0.2 7.0.1, 7.0.0, 6.4.6, 6.4.5, 6.4.4, 6.4.3, 6.4.2, 6.4.1, 6.4.0, 6.2.9, 6.2.8, 6.2.7, 6.2.6, 6.2.5, 6.2.4, 6.2.3, 6.2.2, 6.2.1, 6.2.0, 6.0.10, 6.0.9, 6.0.8, 6.0.7, 6.0.6, 6.0.5, 6.0.4, 6.0.3, 6.0.2, 6.0.1, 6.0.0Listed
Weakness

CWE details

No CWE listed

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