CVE-2019-1687: Cisco Adaptive Security Appliance Software

High severity, CVSS 7.5. EPSS: 2.9% chance of exploitation in the next 30 days.

A vulnerability in the TCP proxy functionality for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to restart unexpectedly, resulting in a denial of service (DoS) condition. The vulnerability is due to an error in TCP-based packet inspection, which could cause the TCP packet to have an invalid Layer 2 (L2)-formatted header. An attacker could exploit this vulnerability by sending a crafted TCP packet sequence to the targeted device. A successful exploit could allow the attacker to cause a DoS condition.

Affected products

• Cisco Adaptive Security Appliance Software: before 9.4.4.34 (fixed in 9.4.4.34); from 9.5, before 9.6.4.25 (fixed in 9.6.4.25); from 9.7, before 9.8.4 (fixed in 9.8.4); from 9.9, before 9.9.2.50 (fixed in 9.9.2.50); from 9.10, before 9.10.1.17 (fixed in 9.10.1.17)
• Cisco Secure Firewall Threat Defense: from 6.0.0, before 6.2.3.12 (fixed in 6.2.3.12); from 6.3.0, before 6.3.0.3 (fixed in 6.3.0.3)

Published 2019-05-03. Last modified 2026-08-11.