CVE-2019-5591
A Default Configuration vulnerability in FortiOS may allow an unauthenticated attacker on the same subnet to intercept sensitive information by impersonating the LDAP server.
- CVSS
- 6.5Mediumscored by CISA
- Exploited in the wild
- Yes, in CISA KEV since 3 Nov 2021CISA deadline for US federal agencies: 3 May 2022known use in ransomware campaignsunvetted proof-of-concept code on github
- EPSS
- 18.6%chance of exploitation in the next 30 daystop 3% of scored CVEsFIRST score of 11 Nov 2026
- Fix
- Patch availablesee the advisories in the references
- Published
- 14 Aug 2020analysed here 12 Nov 2026
Do first. Apply updates per vendor instructions. (CISA's required action for this KEV entry)
Summary
Triage
The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.
Affected products
| Product | Affected versions | Vendor says fixed in |
|---|---|---|
| Fortinet Fortinet FortiOS | FortiOS 6.2.0 and below.Vendor says fixed in: not stated |
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
Products named in our analysis
- fortinet:fortios
Fix and mitigation
WAF and other mitigations
Can a WAF block it? No. A function is missing its authentication check. The attack requests look like normal traffic, so a WAF has nothing to match on.
Also consider: patch
Based on the weakness type only; no CVE-specific evidence yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Remediation steps (AI-written)
Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.
Exploitation evidence
- CISA KEV catalog
- Listed since 3 Nov 2021. Known use in ransomware campaigns.
- CISA due date
- 3 May 2022, the remediation deadline for US federal agencies
- CISA required action
- Apply updates per vendor instructions.
- Public exploit code
- Unvetted proof-of-concept code on GitHub: 1 GitHub proof of concept · 1 Nuclei template
- CISA SSVC
- exploitation active, automatable no, technical impact partialAssessed by CISA 22 Apr 2021 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.
Nuclei
- FortiOS - Insecure LDAP Configuration Detectiondetection template, medium
GitHub proofs of concept
Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.
Timeline
- 14 Aug 2020Published
- 22 Apr 2021CISA SSVC assessment: exploitation active250 days (about 8 months) later
- 3 Nov 2021Added to CISA KEV (exploited in the wild)195 days (about 7 months) later
- 3 May 2022CISA remediation due date (US federal agencies)181 days (about 6 months) later
- 16 Oct 2025First proof-of-concept repository on GitHub (unvetted)1,262 days (about 3 years) later
- 15 Aug 2026CVE record last updated303 days (about 10 months) later
- 12 Nov 2026Analysed by vulneraibility.com89 days (about 3 months) later
CVSS vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
| Metric | Value | What it means |
|---|---|---|
| Attack vector | AdjacentSame subnet or link layer. | Same subnet or link layer. |
| Attack complexity | LowRepeatable attack, no special conditions. | Repeatable attack, no special conditions. |
| Privileges required | NoneThe attacker needs no prior access. | The attacker needs no prior access. |
| User interaction | NoneNo victim action needed. | No victim action needed. |
| Scope | UnchangedImpact stays within the vulnerable component. | Impact stays within the vulnerable component. |
| Confidentiality | HighTotal data disclosure possible. | Total data disclosure possible. |
| Integrity | NoneNo unauthorised modification. | No unauthorised modification. |
| Availability | NoneThe service stays up. | The service stays up. |
Common questions
Is CVE-2019-5591 being exploited?
Yes. CVE-2019-5591 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2019-5591?
CVE-2019-5591 is rated Medium with a CVSS score of 6.5. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2019-5591?
Yes. A fix has been recorded for CVE-2019-5591. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2019-5591 affect?
CVE-2019-5591 affects fortinet:fortios. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
References
2 references in the CVE record, grouped by the tags the record gives them.
Other links (2)
- fortiguard.com /psirt/FG-IR-19-037
- cisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2019-5591
Where the data on this page comes from
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- Nuclei templates: detection templates
- PoC-in-GitHub: GitHub repositories that claim a proof of concept
Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.
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