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CVE Record

CVE-2021-36190: A unintended proxy or intermediary ('confused deputy') in Fortinet FortiWeb version 6.4.1 and below, 6.3.15...

A unintended proxy or intermediary ('confused deputy') in Fortinet FortiWeb version 6.4.1 and below, 6.3.15 and below allows an unauthenticated attacker to access protected hosts via crafted HTTP requests.

MediumCVSS 5.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

FortiWeb could be tricked into acting as an unintended intermediary, letting an attacker reach protected hosts through crafted HTTP requests. The listed severity is medium, but exposure matters because FortiWeb often sits in front of sensitive web applications.

Executive priority

Prioritize remediation for FortiWeb instances protecting sensitive, internal, or business-critical applications. This is not presented as critical or actively exploited in the supplied sources, but the placement of FortiWeb can make bypass-style access issues operationally important.

Technical view

CVE-2021-36190 is a confused-deputy issue in Fortinet FortiWeb. The provided description says crafted HTTP requests can allow access to protected hosts. Affected versions include FortiWeb 6.4.1 and below, 6.3.15 and below, and older listed 6.x releases.

Likely exposure

Organizations running Fortinet FortiWeb 6.4.1, 6.3.15, or older listed 6.x versions may be exposed, especially where FortiWeb fronts internal or restricted web services. The bundle does not identify cloud services, appliances beyond FortiWeb, or non-Fortinet products as affected.

Exploitation context

The source bundle does not show CISA KEV listing or cited active exploitation. The CVSS vector includes exploit maturity P, but the bundle does not provide exploit details. Treat this as credible but not confirmed actively exploited from the supplied evidence.

Researcher notes

There is an evidence inconsistency: the description says unauthenticated attacker, while the provided CVSS vector includes PR:L. Do not assume exploitability beyond the supplied advisory and CVE data. Focus validation on version exposure and unintended backend reachability.

Mitigation direction

  • Check Fortinet advisory FG-IR-21-123 for the vendor-approved fixed FortiWeb release.
  • Upgrade affected FortiWeb versions according to Fortinet guidance.
  • Restrict unnecessary network paths from FortiWeb to protected hosts.
  • Review FortiWeb policies protecting internal or sensitive applications.
  • Monitor FortiWeb and backend logs for unusual HTTP request routing.

Validation and detection

  • Inventory all FortiWeb appliances and record exact firmware versions.
  • Compare versions against the affected list in the CVE source bundle.
  • Confirm vendor remediation has been applied where affected versions exist.
  • Review backend access logs for unexpected requests routed through FortiWeb.
  • Verify protected hosts are not reachable beyond intended FortiWeb policy paths.
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-2021-36190 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L/E:P/RL:X/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
5.5CVSS 3.1MediumCVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L/E:P/RL:X/RC:C2.13.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

5.5Medium
CVSS 3.1 vector shape for CVE-2021-36190Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L/E:P/RL:X/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 FortiWebFortiWeb 6.4.1, 6.4.0, 6.3.15, 6.3.14, 6.3.13, 6.3.12, 6.3.11, 6.3.10, 6.3.9, 6.3.8, 6.3.7, 6.3.6, 6.3.5, 6.3.4, 6.3.3, 6.3.2, 6.3.1, 6.3.0, 6.2.6, 6.2.5, 6.2.4, 6.2.3, 6.2.2, 6.2.1, 6.2.0, 6.1.2, 6.1.1, 6.1.0, 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.