Apache Foundation

The Opossum attack exploits a sophisticated cross-protocol application layer desynchronization vulnerability that compromises TLS-based communications. This attack affects critical protocols including HTTP, FTP, POP3, SMTP, LMTP, and NNTP. By leveraging man-in-the-middle positioning, attackers can inject unexpected messages into secure channels, causing persistent desynchronization between clients and servers and breaking the integrity assumptions of encrypted communications. This vulnerability enables session hijacking, content manipulation, and XSS attacks, posing a significant threat to the organization's security.

Source: https://cybersecuritynews.com/opossum-attack/

TPRM report: https://scoringcyber.rankiteo.com/company/the-apache-software-foundation

"id": "the409071125",
"linkid": "the-apache-software-foundation",
"type": "Vulnerability",
"date": "7/2025",
"severity": "100",
"impact": "5",
"explanation": "Attack threatening the organization's existence"

{'affected_entities': [{'industry': 'Technology', 'type': 'Server'}],
 'attack_vector': 'Man-in-the-Middle',
 'description': 'The Opossum attack is a sophisticated cross-protocol '
                'application layer desynchronization vulnerability that '
                'compromises TLS-based communications by exploiting '
                'differences between implicit and opportunistic TLS '
                'implementations. It affects critical protocols including '
                'HTTP, FTP, POP3, SMTP, LMTP, and NNTP, and enables session '
                'hijacking, content manipulation, and XSS attacks.',
 'impact': {'operational_impact': 'Persistent desynchronization between '
                                  'clients and servers',
            'systems_affected': ['HTTP',
                                 'FTP',
                                 'SMTP',
                                 'POP3',
                                 'LMTP',
                                 'NNTP']},
 'initial_access_broker': {'entry_point': 'Man-in-the-Middle'},
 'lessons_learned': 'Disable opportunistic TLS and prioritize implicit TLS '
                    'implementations to maintain secure communications '
                    'integrity.',
 'motivation': ['Session Hijacking', 'Content Manipulation', 'XSS Attacks'],
 'post_incident_analysis': {'corrective_actions': ['Disable opportunistic TLS',
                                                   'Use implicit TLS only'],
                            'root_causes': 'Differences between implicit and '
                                           'opportunistic TLS implementations'},
 'recommendations': ['Disable opportunistic TLS', 'Use implicit TLS only'],
 'response': {'remediation_measures': ['Disable opportunistic TLS',
                                       'Use implicit TLS only']},
 'title': 'Opossum Attack',
 'type': 'Cross-protocol Application Layer Desynchronization',
 'vulnerability_exploited': ['Implicit TLS', 'Opportunistic TLS']}