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CVE Record

CVE-2021-36167: An improper authorization vulnerabiltiy [CWE-285] in FortiClient Windows versions 7.0.0 and 6.4.6 and below...

An improper authorization vulnerabiltiy [CWE-285] in FortiClient Windows versions 7.0.0 and 6.4.6 and below and 6.2.8 and below may allow an unauthenticated attacker to bypass the webfilter control via modifying the session-id paramater.

MediumCVSS 4.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This CVE affects Fortinet FortiClient for Windows and may let an unauthenticated local attacker bypass web filtering controls by altering a session-id parameter. The impact is mainly loss of an endpoint policy control, not direct data theft or system takeover based on the supplied sources.

Executive priority

Treat as a policy-control bypass issue with moderate urgency. It is less severe than remote code execution, but matters if FortiClient web filtering is part of security, compliance, or acceptable-use enforcement.

Technical view

CVE-2021-36167 is an improper authorization issue, described as CWE-285, in FortiClient Windows 7.0.0, 6.4.6 and below, and 6.2.8 and below. CVSS 3.1 is 4.3 with local attack vector, low complexity, no privileges, no user interaction, scope changed, and low availability impact.

Likely exposure

Organizations are exposed where managed or unmanaged Windows endpoints run the listed FortiClient versions and rely on FortiClient webfilter control. The supplied CVSS vector indicates local exposure, not a remote network-facing service.

Exploitation context

The source bundle does not show CISA KEV listing or confirmed active exploitation. It states exploit code maturity as proof-of-concept in the CVSS metadata, but provides no exploit details and no public exploitation evidence.

Researcher notes

Evidence is limited to CVE metadata and Fortinet’s advisory reference. Avoid assuming affected macOS, Linux, VPN, EMS, or FortiGate products. The supplied description names only FortiClient Windows and does not include detailed fixes or exploitation telemetry.

Mitigation direction

  • Inventory FortiClient Windows versions across all managed endpoints.
  • Check Fortinet advisory FG-IR-20-127 for fixed or recommended versions.
  • Upgrade affected clients according to Fortinet guidance.
  • Prioritize endpoints where web filtering enforces business or compliance policy.
  • Ensure endpoint management blocks unsupported FortiClient versions.

Validation and detection

  • Confirm whether any endpoints run versions listed as affected.
  • Verify FortiClient webfilter control is enabled where expected.
  • Confirm upgraded clients match Fortinet’s fixed-version guidance.
  • Review endpoint compliance reports for unmanaged or stale clients.
  • Run post-upgrade functional checks for webfilter policy enforcement.
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-2021-36167 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
Medium
CVSS
4.3 (3.1)
Known Exploited
No
Published

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

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:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L/E:P/RL:X/RC:X2.51.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

4.3Medium
CVSS 3.1 vector shape for CVE-2021-36167Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

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 7.0.0, 6.4.6, 6.4.5, 6.4.4, 6.4.3, 6.4.2, 6.4.1, 6.4.0, 6.2.8, 6.2.7, 6.2.6, 6.2.5, 6.2.4, 6.2.3, 6.2.2, 6.2.1, 6.2.0Listed
Weakness

CWE details

No CWE listed

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