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High severity8.6NVD Advisory· Published Oct 27, 2021· Updated Aug 11, 2026

CVE-2021-34781

CVE-2021-34781

Description

A vulnerability in the processing of SSH connections for multi-instance deployments of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on the affected device. This vulnerability is due to a lack of proper error handling when an SSH session fails to be established. An attacker could exploit this vulnerability by sending a high rate of crafted SSH connections to the instance. A successful exploit could allow the attacker to cause resource exhaustion, which causes a DoS condition on the affected device. The device must be manually reloaded to recover.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

Affected products

19
  • Cisco Systems, Inc./Firepower Management Center Virtual Appliance8 versions
    cpe:2.3:a:cisco:firepower_management_center_virtual_appliance:6.3.0:*:*:*:*:*:*:*+ 7 more
    • cpe:2.3:a:cisco:firepower_management_center_virtual_appliance:6.3.0:*:*:*:*:*:*:*
    • cpe:2.3:a:cisco:firepower_management_center_virtual_appliance:6.4.0.13:*:*:*:*:*:*:*
    • cpe:2.3:a:cisco:firepower_management_center_virtual_appliance:6.4.0:*:*:*:*:*:*:*
    • cpe:2.3:a:cisco:firepower_management_center_virtual_appliance:6.5.0:*:*:*:*:*:*:*
    • cpe:2.3:a:cisco:firepower_management_center_virtual_appliance:6.6.0:*:*:*:*:*:*:*
    • cpe:2.3:a:cisco:firepower_management_center_virtual_appliance:6.7.0.3:*:*:*:*:*:*:*
    • cpe:2.3:a:cisco:firepower_management_center_virtual_appliance:6.7.1:*:*:*:*:*:*:*
    • cpe:2.3:a:cisco:firepower_management_center_virtual_appliance:7.0.0:*:*:*:*:*:*:*
  • Cisco Systems, Inc./Secure Firewall Threat Defense
    cpe:2.3:a:cisco:secure_firewall_threat_defense:*:*:*:*:*:*:*:*
    Range: >=6.3.0,<6.4.0.13
  • Cisco Systems, Inc./Sourcefire Defense Center8 versions
    cpe:2.3:a:cisco:sourcefire_defense_center:6.3.0:*:*:*:*:*:*:*+ 7 more
    • cpe:2.3:a:cisco:sourcefire_defense_center:6.3.0:*:*:*:*:*:*:*
    • cpe:2.3:a:cisco:sourcefire_defense_center:6.4.0.13:*:*:*:*:*:*:*
    • cpe:2.3:a:cisco:sourcefire_defense_center:6.4.0:*:*:*:*:*:*:*
    • cpe:2.3:a:cisco:sourcefire_defense_center:6.5.0:*:*:*:*:*:*:*
    • cpe:2.3:a:cisco:sourcefire_defense_center:6.6.0:*:*:*:*:*:*:*
    • cpe:2.3:a:cisco:sourcefire_defense_center:6.7.0.3:*:*:*:*:*:*:*
    • cpe:2.3:a:cisco:sourcefire_defense_center:6.7.1:*:*:*:*:*:*:*
    • cpe:2.3:a:cisco:sourcefire_defense_center:7.0.0:*:*:*:*:*:*:*
  • Cisco Systems, Inc./Firepower Threat Defense Softwarellm-fuzzy
  • Cisco Systems, Inc./Adaptive Security Appliance Cx Context Aware Security Softwarecpe-rescue
    Range: n/a

Patches

Vulnerability mechanics

References

1

News mentions

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