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

CVE-2021-34783

Description

A vulnerability in the software-based SSL/TLS message handler of Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition. This vulnerability is due to insufficient validation of SSL/TLS messages when the device performs software-based SSL/TLS decryption. An attacker could exploit this vulnerability by sending a crafted SSL/TLS message to an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition. Note: Datagram TLS (DTLS) messages cannot be used to exploit this vulnerability.

AI Insight

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

Affected products

Cisco Systems, Inc./Secure Firewall Threat Defense
cpe:2.3:a:cisco:secure_firewall_threat_defense:*:*:*:*:*:*:*:*
Range: >=6.4.0,<6.4.0.13
Cisco Systems, Inc./Cisco Adaptive Security Appliance
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
Range: >=9.8.0,<9.8.4.40
Cisco Systems, Inc./Asa 5505 Firmware2 versions
cpe:2.3:o:cisco:asa_5505_firmware:009.016\(001.025\):*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5505_firmware:009.016\(001.025\):*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5505_firmware:009.016\(001\):*:*:*:*:*:*:*
Cisco Systems, Inc./Asa 5512 X Firmware2 versions
cpe:2.3:o:cisco:asa_5512-x_firmware:009.016\(001.025\):*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5512-x_firmware:009.016\(001.025\):*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5512-x_firmware:009.016\(001\):*:*:*:*:*:*:*
Cisco Systems, Inc./Asa 5515 X Firmware2 versions
cpe:2.3:o:cisco:asa_5515-x_firmware:009.016\(001.025\):*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5515-x_firmware:009.016\(001.025\):*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5515-x_firmware:009.016\(001\):*:*:*:*:*:*:*
Cisco Systems, Inc./Asa 5525 X Firmware2 versions
cpe:2.3:o:cisco:asa_5525-x_firmware:009.016\(001.025\):*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5525-x_firmware:009.016\(001.025\):*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5525-x_firmware:009.016\(001\):*:*:*:*:*:*:*
Cisco Systems, Inc./Asa 5545 X Firmware2 versions
cpe:2.3:o:cisco:asa_5545-x_firmware:009.016\(001.025\):*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5545-x_firmware:009.016\(001.025\):*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5545-x_firmware:009.016\(001\):*:*:*:*:*:*:*
Cisco Systems, Inc./Asa 5555 X Firmware2 versions
cpe:2.3:o:cisco:asa_5555-x_firmware:009.016\(001.025\):*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5555-x_firmware:009.016\(001.025\):*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5555-x_firmware:009.016\(001\):*:*:*:*:*:*:*
Cisco Systems, Inc./Asa 5580 Firmware2 versions
cpe:2.3:o:cisco:asa_5580_firmware:009.016\(001.025\):*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5580_firmware:009.016\(001.025\):*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5580_firmware:009.016\(001\):*:*:*:*:*:*:*
Cisco Systems, Inc./Asa 5585 X Firmware2 versions
cpe:2.3:o:cisco:asa_5585-x_firmware:009.016\(001.025\):*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5585-x_firmware:009.016\(001.025\):*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5585-x_firmware:009.016\(001\):*:*:*:*:*:*:*
Cisco Systems, Inc./Adaptive Security Appliance (ASA) Softwarellm-fuzzy
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

tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-tls-decrypt-dos-BMxYjm8MnvdVendor Advisory

News mentions

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