Security readout for executives and security teams
Plain-English summary
Fortinet FortiOS SSL VPN versions listed in the source could let a user bypass the FortiToken second factor by changing username letter case. Because SSL VPN is often internet-facing and CISA lists this CVE in KEV, treat exposed affected systems as urgent.
Executive priority
High priority. This affects VPN authentication, can bypass a second factor, and appears in CISA KEV. Treat vulnerable internet-facing systems as immediate remediation candidates and track completion to closure.
Technical view
CVE-2020-12812 is CWE-287 improper authentication in FortiOS SSL VPN. Affected versions are FortiOS 6.4.0, 6.2.0 through 6.2.3, and 6.0.9 and below. The described failure allows successful login without the FortiToken prompt when username case is changed.
Likely exposure
Exposure is most likely where FortiOS SSL VPN is enabled on the affected versions and FortiToken is used for second-factor authentication. Internet-facing VPN portals raise urgency. The source bundle does not identify affected appliances beyond Fortinet FortiOS.
Exploitation context
CISA KEV inclusion supports known exploitation. The bundle does not provide exploit timing, attacker groups, prevalence, or technical exploit details. The CVSS 9.8 vector indicates network reachability, low complexity, no privileges, and no user interaction.
Researcher notes
The provided evidence supports authentication bypass by username case manipulation, affected FortiOS ranges, critical CVSS, and KEV status. It does not include fixed versions, exploit samples, or environmental prerequisites beyond SSL VPN and FortiToken.
Mitigation direction
- Inventory FortiOS SSL VPN systems and compare versions against the affected range.
- Check Fortinet PSIRT FG-IR-19-283 for vendor remediation guidance and fixed versions.
- Prioritize upgrading or retiring affected SSL VPN deployments per vendor guidance.
- Restrict SSL VPN exposure until remediation is complete where operationally feasible.
- Review authentication logs for username case variants and unexpected VPN sessions.
Validation and detection
- Confirm whether SSL VPN is enabled on each FortiOS device.
- Record FortiOS versions and identify 6.4.0, 6.2.0-6.2.3, or 6.0.9 and below.
- Verify FortiToken enforcement status for SSL VPN users.
- Search VPN authentication logs for successful logins using altered username casing.
- Check whether each affected device has been remediated per Fortinet guidance.
Public sources used
Michael Williams reviewed this cited source version on .
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-287: Credential and account abuse lookup
Authentication and credential weaknesses can make valid-account abuse and credential telemetry useful review starting points. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2020-12812 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CISA KEV status
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://fortiguard.com/psirt/FG-IR-19-283CVE reference · x_refsource_MISC
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-12812CVE reference · government-resource
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Authentication
Improper Authentication represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.