CVE-2020-3196: Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software SSL/TLS Denial of Service Vulnerability

Severity: high (CVSS 8.6 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-05-06 · updated 2026-08-11
Weakness: CWE-400

Description

A vulnerability in the Secure Sockets Layer (SSL)/Transport Layer Security (TLS) handler of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to exhaust memory resources on the affected device, leading to a denial of service (DoS) condition. The vulnerability is due to improper resource management for inbound SSL/TLS connections. An attacker could exploit this vulnerability by establishing multiple SSL/TLS connections with specific conditions to the affected device. A successful exploit could allow the attacker to exhaust the memory on the affected device, causing the device to stop accepting new SSL/TLS connections and resulting in a DoS condition for services on the device that process SSL/TLS traffic. Manual intervention is required to recover an affected device.

Affected products

Cisco ASA Software: from 9.6 before 9.6.4.40; from 9.8 before 9.8.4.20; from 9.9 before 9.9.2.66; from 9.10 before 9.10.1.37; from 9.12 before 9.12.3.2; from 9.13 before 9.13.1.7 — fixed in 9.10.1.37, 9.12.3.2, 9.13.1.7, 9.6.4.40, 9.8.4.20, 9.9.2.66
Cisco Asa 5505 Firmware: 9.4(4), 9.8(4.18), 100.13(0)
Cisco Asa 5510 Firmware: 9.4(4), 9.8(4.18), 100.13(0)
Cisco Asa 5512-X Firmware: 9.4(4), 9.8(4.18), 100.13(0)
Cisco Asa 5515-X Firmware: 9.4(4), 9.8(4.18), 100.13(0)
Cisco Asa 5520 Firmware: 9.4(4), 9.8(4.18), 100.13(0)
Cisco Asa 5525-X Firmware: 9.4(4), 9.8(4.18), 100.13(0)
Cisco Asa 5540 Firmware: 9.4(4), 9.8(4.18), 100.13(0)
Cisco Asa 5545-X Firmware: 9.4(4), 9.8(4.18), 100.13(0)
Cisco Asa 5550 Firmware: 9.4(4), 9.8(4.18), 100.13(0)
Cisco Asa 5555-X Firmware: 9.4(4), 9.8(4.18), 100.13(0)
Cisco Asa 5580 Firmware: 9.4(4), 9.8(4.18), 100.13(0)
Cisco Asa 5585-X Firmware: 9.4(4), 9.8(4.18), 100.13(0)
Cisco Firepower Threat Defense Software: from 6.2.3 before 6.2.3.16; from 6.3.0 before 6.3.0.6; from 6.4.0 before 6.4.0.9; from 6.5.0 before 6.5.0.5 — fixed in 6.2.3.16, 6.3.0.6, 6.4.0.9, 6.5.0.5

How to fix

Upgrade to a fixed version: Cisco ASA Software 9.10.1.37, 9.12.3.2, 9.13.1.7, 9.6.4.40; Cisco Firepower Threat Defense Software 6.2.3.16, 6.3.0.6, 6.4.0.9, 6.5.0.5. Check the vendor advisory for mitigations.

References

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