CVE-2020-3529: Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software SSL VPN Direct Memory Access Denial of Service Vulnerability

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-10-21 · updated 2026-08-11
Weakness: CWE-400

Description

A vulnerability in the SSL VPN negotiation process for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to inefficient direct memory access (DMA) memory management during the negotiation phase of an SSL VPN connection. An attacker could exploit this vulnerability by sending a steady stream of crafted Datagram TLS (DTLS) traffic to an affected device. A successful exploit could allow the attacker to exhaust DMA memory on the device and cause a DoS condition.

Affected products

Cisco Adaptive Security Appliance: before 9.6.4.45 — fixed in 9.6.4.45
Cisco ASA Software: from 9.8.0 before 9.8.4.29; from 9.9.0 before 9.9.2.80; from 9.10.0 before 9.10.1.44; from 9.12.0 before 9.12.4.4; from 9.13.0 before 9.13.1.13; from 9.14.0 before 9.14.1.30 — fixed in 9.10.1.44, 9.12.4.4, 9.13.1.13, 9.14.1.30, 9.8.4.29, 9.9.2.80
Cisco Firepower Threat Defense Software: before 6.3.0.6; from 6.4.0 before 6.4.0.10; from 6.5.0 before 6.5.0.5; from 6.6.0 before 6.6.1 — fixed in 6.3.0.6, 6.4.0.10, 6.5.0.5, 6.6.1

How to fix

Upgrade to a fixed version: Cisco Adaptive Security Appliance 9.6.4.45; Cisco ASA Software 9.10.1.44, 9.12.4.4, 9.13.1.13, 9.14.1.30; Cisco Firepower Threat Defense Software 6.3.0.6, 6.4.0.10, 6.5.0.5, 6.6.1. Check the vendor advisory for mitigations.

References

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