---
id: "CVE-2020-12812"
kind: "vulnerability"
aliases: ["CVE-2020-12812"]
title: "Fortinet FortiOS: Fortinet FortiOS SSL VPN Improper Authentication Vulnerability"
severity: "critical"
cvss: 9.8
epss: 0.45379
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Fortinet FortiOS", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["exploited", "fortios", "fortitoken", "infrastructure", "ransomware", "ssl-vpn"]
not_affected_if: ["no-fortitoken-2fa", "no-ssl-vpn"]
published_at: "2020-07-24T23:15:12+00:00"
first_seen_at: "2026-10-23T19:11:53+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2020-12812", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2020-12812", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2020-12812", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Fortinet FortiOS: Fortinet FortiOS SSL VPN Improper Authentication Vulnerability

Fortinet FortiOS SSL VPN can let a user log in without the second factor (FortiToken) when the username's letter case is changed. An attacker with a valid username and password gets VPN access without the one-time code.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Fortinet FortiOS affected ? fixed ?

## Fix

Apply the FortiOS update per Fortinet's vendor instructions; the sources do not name the fixed version.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2020-12812
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2020-12812
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2020-12812

## From the sources

Fortinet FortiOS SSL VPN contains an improper authentication vulnerability that may allow a user to login successfully without being prompted for the second factor of authentication (FortiToken) if they change the case in their username.

CISA required action: Apply updates per vendor instructions.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_