# CVE-2019-5591: Fortinet FortiOS Default Configuration

> An unauthenticated attacker on the same subnet can intercept sensitive information by impersonating the LDAP server due to default configuration settings.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Yes, since 3 Nov 2021 (CISA KEV), used in ransomware
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Aug 2020
- **Updated:** 15 Aug 2026
- **Also known as:** GHSA-p9g8-h33v-mg42

## What is CVE-2019-5591?

CVE-2019-5591 is a medium-severity vulnerability in Fortinet Fortios, published on 14 Aug 2020. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

Weakness: CWE-306 (Missing Authentication for Critical Functionality)

## Which versions are affected by CVE-2019-5591?

It affects 1 product.


Products: Fortinet Fortios.

## How do I fix CVE-2019-5591?

No fix has been published for CVE-2019-5591 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 3 May 2022.

## Is CVE-2019-5591 being exploited?

Yes. Attackers have exploited CVE-2019-5591 in the wild since at least 3 Nov 2021, including in ransomware campaigns.

Public exploit code:

- The default configuration of LDAP on FortiOS v6.0.x to v6.2.0 does not check server identity for LDAP/S leading to MITM attacks. This PoC demos full exfiltration of credentials sent on the local subnet to an LDAP server that is easily impersonated.  (github_poc): https://github.com/ayewo/fortios-ldap-mitm-poc-CVE-2019-5591
- FortiOS - Insecure LDAP Configuration Detection (nuclei): http/cves/2019/CVE-2019-5591.yaml

## Other vulnerabilities in Fortinet Fortios

- [CVE-2024-23113](https://insights.sbomify.com/CVE-2024-23113/): Fortinet Multiple Products Format String (critical 9.8, exploited in the wild)
- [CVE-2022-40684](https://insights.sbomify.com/CVE-2022-40684/): Fortinet Multiple Products Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2024-55591](https://insights.sbomify.com/CVE-2024-55591/): Fortinet FortiOS and FortiProxy Authentication Bypass (critical 9.6, exploited in the wild)
- [CVE-2024-21762](https://insights.sbomify.com/CVE-2024-21762/): Fortinet FortiOS Out-of-Bound Write (critical 9.6, exploited in the wild)
- [CVE-2022-42475](https://insights.sbomify.com/CVE-2022-42475/): Fortinet FortiOS Heap-Based Buffer Overflow (critical 9.3, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-5591 and fix it if it is affected.

What it is: CVE-2019-5591 is a medium-severity vulnerability in Fortinet Fortios, published on 14 Aug 2020. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2019-5591 in the wild since at least 3 Nov 2021, including in ransomware campaigns.

Affected product: Fortinet Fortios. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2019-5591/ (Markdown: https://insights.sbomify.com/CVE-2019-5591/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-5591
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-5591
- OSV: https://osv.dev/vulnerability/CVE-2019-5591

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-5591/
Summaries are generated and may contain mistakes; the official description above is the record.