CVE-2020-3533: Cisco Secure Firewall Threat Defense

High severity, CVSS 7.5. EPSS: 1.8% chance of exploitation in the next 30 days.

A vulnerability in the Simple Network Management Protocol (SNMP) input packet processor of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to restart unexpectedly. The vulnerability is due to a lack of sufficient memory management protections under heavy SNMP polling loads. An attacker could exploit this vulnerability by sending a high rate of SNMP requests to the SNMP daemon through the management interface on an affected device. A successful exploit could allow the attacker to cause the SNMP daemon process to consume a large amount of system memory over time, which could then lead to an unexpected device restart, causing a denial of service (DoS) condition. This vulnerability affects all versions of SNMP.

Affected products

• Cisco Secure Firewall Threat Defense: before 6.3.0.6 (fixed in 6.3.0.6); from 6.4.0, before 6.4.0.10 (fixed in 6.4.0.10); from 6.5.0, before 6.5.0.5 (fixed in 6.5.0.5); from 6.6.0, before 6.6.1 (fixed in 6.6.1)

Published 2020-10-21. Last modified 2026-08-11.