CVE-2020-12812

critical

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.

From the Tenable Blog

CVE-2018-13379, CVE-2019-5591, CVE-2020-12812: Fortinet Vulnerabilities Targeted by APT Actors

Published: 2021-04-08

Threat actors and ransomware groups are actively targeting three legacy Fortinet vulnerabilities. Background On April 2, the Federal Bureau of Investigation (FBI) along with the Cybersecurity and Infrastructure Security Agency (CISA) issued a joint cybersecurity advisory regarding activity involving advanced persistent threat (APT) actors.

References

https://www.bleepingcomputer.com/news/security/over-10-000-fortinet-firewalls-exposed-to-ongoing-2fa-bypass-attacks/

https://www.securityweek.com/fortinet-warns-of-new-attacks-exploiting-old-vulnerability/

https://www.bleepingcomputer.com/news/security/fortinet-warns-of-5-year-old-fortios-2fa-bypass-still-exploited-in-attacks/

https://thehackernews.com/2025/12/fortinet-warns-of-active-exploitation.html

https://securityaffairs.com/186117/security/five-year-old-fortinet-fortios-ssl-vpn-flaw-actively-exploited.html

https://www.theregister.com/2025/06/04/play_ransomware_infects_900_victims/

https://www.cisa.gov/news-events/cybersecurity-advisories/aa23-352a

https://duo.com/decipher/hive-ransomware-attacks-target-fortios-microsoft-exchange-flaws

https://www.tenable.com/cyber-exposure/a-look-inside-the-ransomware-ecosystem

https://www.tenable.com/cyber-exposure/2021-threat-landscape-retrospective

https://www.cisa.gov/sites/default/files/publications/AA21-321A-Iranian%20Government-Sponsored%20APT%20Actors%20Exploiting%20Microsoft%20Exchange%20and%20Fortinet%20Vulnerabilities.pdf

https://web.archive.org/web/20211025233339/https://twitter.com/pancak3lullz/status/1452679527197560837

https://www.cisa.gov/news-events/cybersecurity-advisories/aa21-209a

https://www.ic3.gov/Media/News/2021/210402.pdf

https://www.trendmicro.com/vinfo/us/security/news/ransomware-spotlight/ransomware-spotlight-play

https://www.tenable.com/blog/frequently-asked-questions-about-iranian-cyber-operations

https://www.tenable.com/blog/cve-2024-55591-fortinet-authentication-bypass-zero-day-vulnerability-exploited-in-the-wild

https://www.tenable.com/blog/cve-2024-21762-critical-fortinet-fortios-out-of-bound-write-ssl-vpn-vulnerability

https://www.tenable.com/blog/aa22-257a-cybersecurity-joint-advisory-on-iranian-islamic-revolutionary-guard-ransomware

https://www.tenable.com/blog/hold-the-door-why-organizations-need-to-prioritize-patching-ssl-vpns

https://www.tenable.com/blog/cve-2018-13379-cve-2019-5591-cve-2020-12812-fortinet-vulnerabilities-targeted-by-apt-actors

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-12812

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

Details

Source: Mitre, NVD

Published: 2020-07-24

Updated: 2025-10-24

Known Exploited Vulnerability (KEV)

Risk Information

CVSS v2

Base Score: 7.5

Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P

Severity: High

CVSS v3

Base Score: 9.8

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Severity: Critical

EPSS

EPSS: 0.46006

Vulnerability Watch

Tenable Research has classified this CVE under the following Vulnerability Watch classification, which includes active and historical (inactive) classifications. You can learn more about these classifications on our blog.

Vulnerability of Interest

Detections

Analytics