CVE-2019-5591Fortinet FortiOS Default Configuration Vulnerability
CVE-2019-5591 is a missing authentication in Fortinet FortiOS, rated medium (6.5 on CVSS 3.1).
Why this priority: Exploited in the wild: listed in CISA's KEV catalog.
Published · Updated · NVD status: Analyzed
What it is
A function that should require sign-in can be called by anyone.
How it is reached
An attacker can exploit it from the same local network segment, without an account, and nobody has to click anything.
What an attacker gains
A successful attack can read the data it protects. In practice, this kind of flaw lets an attacker act as a signed-in user, or an administrator, without valid credentials.
Is it being exploited?
CISA added it to the Known Exploited Vulnerabilities catalog on 2021-11-03: it is being exploited in the wild. CISA links it to ransomware campaigns. EPSS estimates a 19% chance of exploitation activity in the next 30 days, higher than 97% of scored CVEs.
What to do
- Treat it as urgent: it is on CISA's KEV list. CISA's deadline for US federal agencies: 2022-05-03.
- No fixed version is listed yet. Find every place Fortinet FortiOS runs, watch the references for a fix, and plan a replacement if it is no longer supported.
- Segment the networks that can reach it.
- Check exposed instances for signs of compromise, not only for the version.
Description from NVD
A Default Configuration vulnerability in FortiOS may allow an unauthenticated attacker on the same subnet to intercept sensitive information by impersonating the LDAP server.
What this means for your architecture.
A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.
Components it touches
- Network edge devices: VPNs, firewalls, routers and gateways. They sit between the internet and internal networks, so a flaw in one is often the first step into everything behind it.
- Operating systems on servers, workstations or devices. Everything on the host inherits the flaw.
- Sign-in, session and token handling. The flaw sits between anonymous callers and authenticated sessions.
- Identity providers and SSO. The flaw sits between anonymous callers and authenticated sessions.
Trust boundaries in play
- Local network segment. The attacker must share a network segment with the target.
- Between anonymous callers and authenticated sessions. An attacker who crosses it can act as a signed-in user, or an administrator, without valid credentials.
Questions to answer about your own systems
- Where does Fortinet FortiOS run in your systems, and at which version?
- Which network segments can reach them?
- What can it reach once compromised: which data stores, secrets and services?
Sources
- CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
- Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
- Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
- Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.