CVE-2021-34792: Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Resource Exhaustion Denial of Service Vulnerability

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-10-27 · updated 2026-08-11
Weakness: CWE-400

Description

A vulnerability in the memory management of Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper resource management when connection rates are high. An attacker could exploit this vulnerability by opening a significant number of connections on an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

Affected products

Cisco ASA Software: from 9.8.0 before 9.8.4.40; from 9.12.0 before 9.12.4.29; from 9.14.0 before 9.14.3.9; from 9.15.0 before 9.15.1.17; from 9.16.0 before 9.16.2.3 — fixed in 9.12.4.29, 9.14.3.9, 9.15.1.17, 9.16.2.3, 9.8.4.40
Cisco Asa 5505 Firmware: 009.014(001.150), 099.017(001.211), 099.017(001.220), 099.017(015.050)
Cisco Asa 5512-X Firmware: 009.014(001.150), 099.017(001.211), 099.017(001.220), 099.017(015.050)
Cisco Asa 5515-X Firmware: 009.014(001.150), 099.017(001.211), 099.017(001.220), 099.017(015.050)
Cisco Asa 5525-X Firmware: 009.014(001.150), 099.017(001.211), 099.017(001.220), 099.017(015.050)
Cisco Asa 5545-X Firmware: 009.014(001.150), 099.017(001.211), 099.017(001.220), 099.017(015.050)
Cisco Asa 5555-X Firmware: 009.014(001.150), 099.017(001.211), 099.017(001.220), 099.017(015.050)
Cisco Asa 5580 Firmware: 009.014(001.150), 099.017(001.211), 099.017(001.220), 099.017(015.050)
Cisco Asa 5585-X Firmware: 009.014(001.150), 099.017(001.211), 099.017(001.220), 099.017(015.050)
Cisco Firepower Threat Defense Software: from 6.4.0 before 6.4.0.13; from 6.6.0 before 6.6.5; from 6.7.0 before 6.7.0.3; from 7.0.0 before 7.0.1 — fixed in 6.4.0.13, 6.6.5, 6.7.0.3, 7.0.1

How to fix

Upgrade to a fixed version: Cisco ASA Software 9.12.4.29, 9.14.3.9, 9.15.1.17, 9.16.2.3; Cisco Firepower Threat Defense Software 6.4.0.13, 6.6.5, 6.7.0.3, 7.0.1. Check the vendor advisory for mitigations.

References

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