CVE-2020-3255: Cisco ASA 5505 Firmware

High severity, CVSS 7.5. EPSS: 1.9% chance of exploitation in the next 30 days.

A vulnerability in the packet processing functionality of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to inefficient memory management. An attacker could exploit this vulnerability by sending a high rate of IPv4 or IPv6 traffic through an affected device. This traffic would need to match a configured block action in an access control policy. An exploit could allow the attacker to cause a memory exhaustion condition on the affected device, which would result in a DoS for traffic transiting the device, as well as sluggish performance of the management interface. Once the flood is stopped, performance should return to previous states.

Affected products

• Cisco ASA 5505 Firmware: version 9.10(1.3) only
• Cisco ASA 5510 Firmware: version 9.10(1.3) only
• Cisco ASA 5512-X Firmware: version 9.10(1.3) only
• Cisco ASA 5515-X Firmware: version 9.10(1.3) only
• Cisco ASA 5520 Firmware: version 9.10(1.3) only
• Cisco ASA 5525-X Firmware: version 9.10(1.3) only
• Cisco ASA 5540 Firmware: version 9.10(1.3) only
• Cisco ASA 5545-X Firmware: version 9.10(1.3) only
• Cisco ASA 5550 Firmware: version 9.10(1.3) only
• Cisco ASA 5555-X Firmware: version 9.10(1.3) only
• Cisco ASA 5580 Firmware: version 9.10(1.3) only
• Cisco ASA 5585-X Firmware: version 9.10(1.3) only
• Cisco Secure Firewall Threat Defense: from 6.2.3, before 6.2.3.16 (fixed in 6.2.3.16); from 6.3.0, before 6.3.0.6 (fixed in 6.3.0.6); from 6.4.0, before 6.4.0.9 (fixed in 6.4.0.9)

Published 2020-05-06. Last modified 2026-08-11.