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Full vulnerability report · 2026
CVE-2025-53379High confidence

Fortinet FortiAuthenticator: Out-of-bounds Read

Fortinet · FortiAuthenticator

Official source article: Fortinet FG-IR-26-146 ↗. Check the applicable product and release in the original source.

7.0HighCVSS 3.1
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:High, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 0.53% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Fortinet FortiAuthenticator and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 30 daysRemediation target: Within 180 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2025-210464

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

A out-of-bounds read vulnerability in Fortinet FortiAuthenticator 6.6.0 through 6.6.2, FortiAuthenticator 6.5 all versions may allow a remote unauthenticated attacker to retrieve sensitive information via a specially crafted request.

What

A out-of-bounds read vulnerability in Fortinet FortiAuthenticator 6.6.0 through 6.6.2, FortiAuthenticator 6.5 all versions may allow a remote unauthenticated attacker to retrieve sensitive information via a specially crafted request.

Why

The product reads data past the end, or before the beginning, of the intended buffer.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may obtain information outside the intended access boundary.

What

A out-of-bounds read vulnerability in Fortinet FortiAuthenticator 6.6.0 through 6.6.2, FortiAuthenticator 6.5 all versions may allow a remote unauthenticated attacker to retrieve sensitive information via a specially crafted request.

Why

The product reads data past the end, or before the beginning, of the intended buffer.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may obtain information outside the intended access boundary.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Out-of-bounds Read → obtain information outside the intended access boundary
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-125 ↗

CWE-125: Out-of-bounds Read. The product reads data past the end, or before the beginning, of the intended buffer.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:F/RL:O/RC:C

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.INoneIntegrity impact: No direct loss is represented by this metric.ANoneAvailability impact: No direct loss is represented by this metric.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedCWE-125
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

CERT-FR · French · CERTFR-2026-AVI-0879Multiples vulnérabilités dans les produits Fortinet

De multiples vulnérabilités ont été découvertes dans les produits Fortinet. Certaines d'entre elles permettent à un attaquant de provoquer une exécution de code arbitraire, une élévation de privilèges et une atteinte à la confidentialité des données.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-023882フォーティネットのFortiAuthenticatorにおける境界外読み取りに関する脆弱性

Fortinet FortiAuthenticator 6.6.0から6.6.2、およびFortiAuthenticator 6.5のすべてのバージョンには、境界外読み取りの脆弱性が存在します。この脆弱性によって、リモートの認証されていない攻撃者が特別に細工されたリクエストを介して機密情報を取得できる可能性があります。

Official advisory ↗
NCSC-NL · Dutch · NCSC-2026-0244Kwetsbaarheid verholpen in Fortinet FortiAuthenticator

Fortinet FortiAuthenticator versions 6.5 and 6.6.0 through 6.6.2 contain an out-of-bounds read vulnerability that allows remote unauthenticated attackers to access sensitive information via specially crafted requests.

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
FortiAuthenticator: 6.6.0 ≤ 6.6.2, 6.5.0 ≤ 6.5.7, 6.4.0 ≤ 6.4.11, 6.3.0 ≤ 6.3.5
Fixed
Upgrade to FortiAuthenticator version 6.6.3 or above
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
Official vendor articles1 stored document

Linked articles are downloaded and versioned as source evidence. A CVE mention or approved update relationship does not, by itself, verify a fix for every product branch.

  • PSIRT | FortiGuard Labs →Original publisher ↗Searchable text snapshot · Captured 28 Sep 2026PSIRT Out of bounds read in GUI Summary An out of bounds read [CWE-125] vulnerability in FortiAuthenticator may allow a remote unauthenticated attacker to retrieve sensitive information via a specially crafted request. Version Affected Solution FortiAuthenticator 8.0 Not affected Not Applicable FortiAuthenticator
04

Evidence and provenance

Published 14 Jul 2026 · Last source change 22 Jul 2026, 13:57 UTC · CWE-125 · Out-of-bounds Read

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2025-210464
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Vendor guidanceAuthoritative vendor guidance changed: added remediation: fortiguard.fortinet.com/FG-IR-26-146.
    Before
    vendor advisory: fortiguard.fortinet.com/FG-IR-26-146
    After
    remediation: fortiguard.fortinet.com/FG-IR-26-146 · vendor advisory: fortiguard.fortinet.com/FG-IR-26-146
    psirt@fortinet.com ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    6.6.0 ≤ 6.6.2; 6.5.0 ≤ 6.5.7; 6.4.0 ≤ 6.4.11; 6.3.0 ≤ 6.3.5 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    FortiAuthenticator: 6.6.0 ≤ 6.6.2, 6.5.0 ≤ 6.5.7, 6.4.0 ≤ 6.4.11, 6.3.0 ≤ 6.3.5 · Fixed: Upgrade to FortiAuthenticator version 6.6.3 or above
    CNA ↗
  3. Remediation statusRemediation status changed from Awaiting fix to Patch available.
    Before
    Awaiting fix
    After
    Patch available
    psirt@fortinet.com ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2025-210464↗CVE authority or vendor reference · Fortinet FG-IR-26-146↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2025-53379 · cve.blacktree.nl