CVE-2020-12812 — Fortinet FortiOS SSL VPN Improper Authentication Vulnerability

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.

01What is this vulnerability?

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.

02Affected products

Vendor	Product	Versions
n	a / Fortinet FortiOS	FortiOS 6.4.0, 6.2.0 to 6.2.3, 6.0.9 and below

03Active exploitation status

Yes — actively exploited. Added to the CISA KEV catalog on 2021-11-03. Ransomware use: Known.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Open the Sigma generator with a pre-filled prompt for this CVE to draft a starting detection in your stack of choice:

Open in Sigma generator →

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2020-07-24T22:28:43.000Z
• Last modified: 2025-10-21T23:35:38.889Z
• Added to CISA KEV: 2021-11-03
• BOD 22-01 due: 2022-05-03

09References

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