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Full vulnerability report · 2020
CVE-2019-5591High confidence

Fortinet FortiOS Default Configuration Vulnerability

Fortinet · FortiOS

6.5MediumCVSS 3.1
Recommended action
Mitigate now

CISA confirms exploitation in the wild and lists 2022-05-03 as the remediation due date.

Mitigation available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:Critical, raised 2 bands.upgradedsince 3 Nov 2021

Evidence used

  • CISA confirms exploitation in the wild.
  • EPSS is 18.57% for the current model date.

Compensating controls

  • Apply the linked authoritative mitigation while planning the permanent fix.
  • Restrict local access and enforce least privilege on affected hosts.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs Fortinet FortiOS and falls inside the recorded affected range.
  2. Recheck the vendor advisory before scheduling a change because no verified fixed version is currently retained.
  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 3 daysRemediation target: Within 90 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-2019-15166

CISA KEV mirrored by ENISA

A Default Configuration vulnerability in FortiOS may allow an unauthenticated attacker on the same subnet to intercept sensitive information by impersonating the LDAP server.

EUVD state
Present in the current official mapping
Known exploitation
Recorded by ENISA since 3 Nov 2021. Evidence sources: cisa_kev.
ENISA score
6.5 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionMitigate now

CISA confirms exploitation in the wild and lists 2022-05-03 as the remediation due date.

Mitigation available
01

What, why and how

Fortinet FortiOS contains a default configuration vulnerability that may allow an unauthenticated attacker on the same subnet to intercept sensitive information by impersonating the Lightweight Directory Access Protocol (LDAP) server.

What

Fortinet FortiOS contains a default configuration vulnerability that may allow an unauthenticated attacker on the same subnet to intercept sensitive information by impersonating the Lightweight Directory Access Protocol (LDAP) server.

Why

A security-sensitive function is reachable without the authentication check that should protect it.

How

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

What

Fortinet FortiOS contains a default configuration vulnerability that may allow an unauthenticated attacker on the same subnet to intercept sensitive information by impersonating the Lightweight Directory Access Protocol (LDAP) server.

Why

A security-sensitive function is reachable without the authentication check that should protect it.

How

An attacker operating through the affected interface 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.
Confirmed in the wild

CISA added this CVE to its Known Exploited Vulnerabilities catalogue on 2021-11-03. Known ransomware campaign use is recorded.

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
the affected interface → Missing Authentication for Critical Function → obtain information outside the intended access boundary
Attack surface
Unspecified
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-306 ↗

CWE-306: Missing Authentication for Critical Function. The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.

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

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

AVAdjacentAttack vector: The attacker must be on an adjacent or logically close 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.
UnauthenticatedCWE-306CISA KEV
A

Official authority intelligence

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

ENISA EUVD · EUVD-2019-15166Known-exploited evidence recorded

A Default Configuration vulnerability in FortiOS may allow an unauthenticated attacker on the same subnet to intercept sensitive information by impersonating the LDAP server.

Official EUVD record ↗
Canadian Centre for Cyber Security · English · AL21-005Exploitation of Fortinet FortiOS vulnerabilities (CISA, FBI) - update 1

On 2 April 2021, the Cybersecurity and Infrastructure Security Agency (CISA), the United States’ agency responsible for protecting its critical infrastructure from physical and cyber threats, and the Federal Bureau of Investigation (FBI) issued a Joint Cybersecurity Advisory [ 1 ], drawing attention to recent scanning and exploitation of vulnerabilities within unpatched Fortinet devices. The advisory states that sophisticated actors have been observed scanning for and are believed to be exploiting three specific vulnerabilities in FortiOS: CVE-2018-13379: A path traversal vulnerability in FortiOS CVE-2020-12812: An improper authentication vulnerability in FortiOS SSL VPN CVE-2019-5591: A default configuration vulnerability in FortiOS Fortinet has previously published updates to address all the above vulnerabilities and the Cyber Centre reported on CVE-2018-13379 in August 2019. [ 2 ] The advisory claims that the actors may be using these CVEs alone or in combination to gain access to networks across multiple sectors, including government, commercial and technical services, to pre-position for eventual data exfiltration or data encryption activity. The Cyber Centre would like to highlight this advisory, as it provides important information to system owners and operators responsible for defending their systems and networks from cyber threats. Should activity matching the content of this Alert be discovered, recipients are encouraged to contact the Cyber Centre by email ( contact@cyber.gc.ca ) or by telephone ( 1-833-CYBER-88 or 1-833-292-3788 ). UPDATE 1 On 27 May 2021, in coordination with CISA, the FBI published an FBI FLASH with an updated warning of continued exploitation of vulnerabilities in FortiOS (CVE-2018-13379, CVE-2020-12812, and CVE-2019-5591) by sophisticated actors. The FBI FLASH states that sophisticated actors exploited vulnerabilities in a Fortigate appliance to access a webserver hosting the domain for a U.S. municipal government. Refer to the FBI FLASH for further details and recommended mitigations.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20200819Security Bulletin 19 Aug 2020

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 19 Aug 2020, published on 19 August 2020. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2019-AVI-359Multiples vulnérabilités dans les produits Fortinet

De multiples vulnérabilités ont été découvertes dans les produits Fortinet. Elles permettent à un attaquant de provoquer une exécution de code arbitraire, un déni de service et une atteinte à la confidentialité des données.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2019-015828FortiOS における重要な機能に対する認証の欠如に関する脆弱性

FortiOS には、重要な機能に対する認証の欠如に関する脆弱性が存在します。

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-5709Fortinet 제품 보안 업데이트 권고

FortiOS 제품에서 발생하는 정보 노출 취약점(CVE-2019-5591)[3]

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-5285Fortinet 제품 보안 업데이트 권고

FortiOS에서 취약한 기본설정으로 인해 발생하는 정보노출 취약점(CVE-2019-5591) [2]

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.
Mitigation available
Affected
Fortinet FortiOS: FortiOS 6.2.0 and below.
Fixed
No fixed version is explicitly recorded in the structured CVE data.
Action
Apply the mitigation in the linked authoritative guidance while planning the vendor's permanent fix.
Workaround
A mitigation or workaround reference is available from the source linked below; validate it against the affected product and version.
04

Evidence and provenance

Published 14 Aug 2020 · Last source change 15 Aug 2026, 03:55 UTC · CWE-306 · Missing Authentication for Critical Function

CVE recordCVE.org · 5.2
CVSS sourceNIST NVD
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-2019-15166
Product sourceCISA KEV
Remediation sourceCVE/CNA references
CWE sourceCISA ADP
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. Affected versionsThe structured affected or fixed version information changed.
    Before
    FortiOS 6.2.0 and below. · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    Fortinet FortiOS: FortiOS 6.2.0 and below. · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    CNA ↗
  2. CISA KEV stateCISA KEV now confirms exploitation in the wild.
    Before
    listed in CISA KEV since 2021-11-03
    After
    listed in CISA KEV since 2021-11-03
    CISA KEV ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Added to CISA KEV
Mitigation reference recorded
ENISA EUVD · EUVD-2019-15166↗CISA KEV record↗CVE authority or vendor reference↗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-2019-5591 · cve.blacktree.nl