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CVE Record

CVE-2021-26103: An insufficient verification of data authenticity vulnerability (CWE-345) in the user interface of FortiPro...

An insufficient verification of data authenticity vulnerability (CWE-345) in the user interface of FortiProxy verison 2.0.3 and below, 1.2.11 and below and FortiGate verison 7.0.0, 6.4.6 and below, 6.2.9 and below of SSL VPN portal may allow a remote, unauthenticated attacker to conduct a cross-site request forgery (CSRF) attack . Only SSL VPN in web mode or full mode are impacted by this vulnerability.

MediumCVSS 6.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-26103 affects Fortinet SSL VPN portals when web mode or full mode is used. A remote unauthenticated attacker could trick a user into a CSRF action, causing limited confidentiality, integrity, or availability impact. The source bundle does not confirm active exploitation.

Executive priority

Treat as a moderate-priority perimeter VPN issue. It is not KEV-listed in the supplied data, but internet-facing VPN services deserve prompt review because user interaction could enable unauthorized state-changing actions.

Technical view

The issue is insufficient verification of data authenticity in FortiProxy and FortiGate/FortiOS SSL VPN portal UI. The CVSS 3.1 score is 6.3, with network access, low attack complexity, no privileges, and required user interaction. Impact is limited to SSL VPN web or full mode.

Likely exposure

Exposure is most likely on Fortinet FortiOS/FortiGate or FortiProxy deployments running affected versions with SSL VPN portal web mode or full mode enabled and reachable by users.

Exploitation context

The bundle describes remote unauthenticated CSRF with required user interaction. CISA KEV is false, and no supplied source states active exploitation or public weaponization.

Researcher notes

The affected list is clearer for FortiOS than FortiProxy in the bundle. The provided data does not include fixed versions, detailed attack prerequisites beyond user interaction, or vendor mitigation text, so remediation should be tied to Fortinet guidance.

Mitigation direction

  • Check Fortinet advisory FG-IR-20-158 for fixed releases or official workarounds.
  • Inventory FortiOS, FortiGate, and FortiProxy versions against the affected ranges.
  • Prioritize remediation where SSL VPN web mode or full mode is enabled.
  • Disable unnecessary SSL VPN web or full mode where operationally feasible.
  • Restrict SSL VPN exposure according to vendor and business requirements.

Validation and detection

  • Confirm exact FortiOS or FortiProxy version on each affected appliance.
  • Verify whether SSL VPN web mode or full mode is enabled.
  • Check whether the SSL VPN portal is reachable from untrusted networks.
  • Review vendor advisory status before declaring remediation complete.
  • Document systems not affected because SSL VPN web/full mode is disabled.
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-2021-26103 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
6.3 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L/E:F/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
6.3CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L/E:F/RL:X/RC:X2.83.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

6.3Medium
CVSS 3.1 vector shape for CVE-2021-26103Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L/E:F/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 FortiOSFortiOS 7.0.0, 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, 6.0.14, 6.0.13, 6.0.12, 6.0.11, 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, 6.0.0, 5.6.14, 5.6.13, 5.6.12, 5.6.11, 5.6.10, 5.6.9, 5.6.8, 5.6.7, 5.6.6, 5.6.5, 5.6.4, 5.6.3, 5.6.2, 5.6.1, 5.6.0Listed
Weakness

CWE details

No CWE listed

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