Fortinet: Active Exploitation of FortiOS SSL VPN Vulnerability CVE-2020-12812

**Fortinet Warns of Active Exploitation of 5-Year-Old FortiOS SSL VPN Flaw**

Fortinet has confirmed active exploitation of CVE-2020-12812, a five-year-old improper authentication vulnerability in its FortiOS SSL VPN. The flaw, rated 5.2 (moderate severity) on the CVSS scale, allows attackers to bypass authentication—including two-factor authentication (2FA)—under specific conditions, granting unauthorized system access.

The vulnerability stems from inadequate session management in FortiOS SSL VPN. When a session token expires or terminates unexpectedly, the flaw enables login without a second authentication factor. Exploitation is more likely in environments where 2FA enforcement is inconsistent or session tokens are improperly reused due to misconfigurations.

Fortinet’s recent detection of attacks underscores persistent challenges in legacy system management, as many organizations fail to apply critical patches or enforce secure configurations. The company has issued advisories urging users to update to the latest firmware, conduct regular audits, and prioritize multi-factor authentication (MFA) to mitigate risks.

The incident highlights broader cybersecurity concerns, particularly the dangers of unpatched legacy systems. Security teams are reminded of the need for proactive vulnerability management, continuous monitoring, and adherence to best practices to prevent unauthorized access and data breaches.

Source: https://dailysecurityreview.com/cyber-security/network-security/active-exploitation-of-fortios-ssl-vpn-vulnerability-cve-2020-12812/

Fortinet cybersecurity rating report: https://www.rankiteo.com/company/fortinet

"id": "FOR1767018781",
"linkid": "fortinet",
"type": "Vulnerability",
"date": "12/2025",
"severity": "25",
"impact": "1",
"explanation": "Attack without any consequences"

{'affected_entities': [{'customers_affected': 'Users of FortiOS SSL VPN with '
                                              'vulnerable configurations',
                        'industry': 'Cybersecurity',
                        'name': 'Fortinet',
                        'type': 'Vendor'}],
 'attack_vector': 'SSL VPN',
 'date_publicly_disclosed': '2020',
 'description': 'Fortinet has reported the active exploitation of a '
                'vulnerability in its FortiOS SSL VPN, tracked as '
                'CVE-2020-12812. This improper authentication flaw allows '
                'malicious actors to bypass authentication mechanisms under '
                'specific conditions, gaining unauthorized access to systems. '
                'The vulnerability has a CVSS score of 5.2, indicating '
                'moderate severity.',
 'impact': {'operational_impact': 'Unauthorized system access',
            'systems_affected': 'FortiOS SSL VPN'},
 'lessons_learned': 'Highlights fundamental challenges in managing legacy '
                    'systems and the importance of maintaining a comprehensive '
                    'patching strategy, regular audits, and robust '
                    'multi-factor authentication protocols.',
 'post_incident_analysis': {'corrective_actions': 'Apply security patches, '
                                                  'enforce multi-factor '
                                                  'authentication, conduct '
                                                  'regular audits and threat '
                                                  'assessments',
                            'root_causes': 'Inadequate session management '
                                           'within FortiOS SSL VPN, lack of '
                                           'stringent enforcement of '
                                           'two-factor authentication '
                                           'protocols, improper reuse of '
                                           'session tokens'},
 'recommendations': ['Maintain a consistent update schedule to ensure systems '
                     'run the latest firmware versions',
                     'Conduct regular audits and threat assessments to catch '
                     'misconfigurations early',
                     'Prioritize robust and consistent application of '
                     'multi-factor authentication in user access protocols',
                     'Frequently review current and legacy systems for '
                     'compliance with security best practices'],
 'references': [{'source': 'Fortinet Advisory'}],
 'response': {'communication_strategy': 'Disseminated advisories urging users '
                                        'to apply recent security patches',
              'remediation_measures': 'Apply security patches, enforce '
                                      'multi-factor authentication, conduct '
                                      'regular audits and threat assessments'},
 'stakeholder_advisories': 'Fortinet has disseminated advisories urging users '
                           'to apply recent security patches and follow secure '
                           'configuration practices.',
 'title': 'Active Exploitation of CVE-2020-12812 in FortiOS SSL VPN',
 'type': 'Improper Authentication',
 'vulnerability_exploited': 'CVE-2020-12812'}