Security readout for executives and security teams
Plain-English summary
FortiOS systems at version 6.2.0 or earlier may trust an impostor LDAP server under the default configuration. An unauthenticated attacker on the same network segment could intercept sensitive information. The attack requires adjacent network access, but CISA lists the vulnerability as known exploited.
Executive priority
Treat this as a high-priority remediation despite its medium base severity. Known exploitation and potential disclosure of sensitive information justify prompt action, especially on shared or weakly segmented networks.
Technical view
CVE-2019-5591 is a default-configuration authentication weakness in FortiOS 6.2.0 and earlier. An adjacent, unauthenticated attacker can impersonate the configured LDAP server and compromise confidentiality. CVSS 3.1 is 6.5, with high confidentiality impact but no stated integrity or availability impact.
Likely exposure
Exposure is most likely where FortiOS 6.2.0 or earlier uses LDAP under the vulnerable default configuration and untrusted systems can reach the same subnet. The supplied evidence does not establish how many deployments remain exposed.
Exploitation context
CISA KEV inclusion supports known exploitation in the wild. Exploitation still requires access to the same subnet and the relevant LDAP configuration. The supplied sources provide no campaign, attacker, prevalence, or exploitation-timeline details.
Researcher notes
The adjacent-network vector, low complexity, no privileges, and no user interaction align with CVSS 3.1 score 6.5. CWE-306 indicates missing authentication for a critical function. The bundle does not identify intercepted data types, exploitation mechanics, a fixed release, or vendor-prescribed mitigation details.
Mitigation direction
- Inventory FortiOS versions and identify systems running 6.2.0 or earlier.
- Review LDAP settings against Fortinet advisory FG-IR-19-037.
- Follow current Fortinet guidance for configuration changes or upgrades; the supplied bundle names no fixed version.
- Restrict untrusted access to network segments carrying FortiOS-to-LDAP traffic.
- Prioritize KEV-listed exposed systems for remediation.
Validation and detection
- Confirm each FortiOS version using authoritative asset and device records.
- Determine whether LDAP is configured and whether vulnerable defaults remain enabled.
- Verify network segmentation prevents untrusted hosts from accessing the relevant subnet.
- Review monitoring data for unexpected LDAP endpoints or anomalous authentication traffic.
- After remediation, compare configuration and version status with current Fortinet guidance.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
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
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-306: Credential and account abuse lookup
Authentication and credential weaknesses can make valid-account abuse and credential telemetry useful review starting points. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2019-5591 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.5 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
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.
CISA KEV status
SSVC decision data
CVSS vector scores
1 official scoreWe 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.
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N2.83.6CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
6.5MediumVector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- Added to KEVCISA-ADP
CISA Known Exploited Vulnerabilities metadata lists this CVE as known exploited.
- ADP timelineCISA-ADP
CVE-2019-5591 added to CISA KEV
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
- 2021-11-03T00:00:00.000Z: CVE-2019-5591 added to CISA KEV
Source materials
- CVE List V5 sourceCVE List V5
- https://www.fortiguard.com/psirt/FG-IR-19-037CVE reference, fortinet · x_refsource_CONFIRM
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2019-5591CVE reference, CISA-ADP · government-resource
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Missing Authentication for Critical Function
Missing Authentication for Critical Function represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.