CVE-2019-1694: Cisco Adaptive Security Appliance Software and Cisco Firepower Threat Defense Software TCP Timer Handling Denial of Service Vulnerability

Severity: high (CVSS 8.6 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2019-05-03 · updated 2026-08-11
Weakness: CWE-20

Description

A vulnerability in the TCP processing engine of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition. The vulnerability is due to the improper handling of TCP traffic. An attacker could exploit this vulnerability by sending a specific sequence of packets at a high rate through an affected device. A successful exploit could allow the attacker to temporarily disrupt traffic through the device while it reboots.

Affected products

Cisco ASA Software: before 9.4.4.34; from 9.5 before 9.6.4.25; from 9.7 before 9.8.4; from 9.9 before 9.9.2.50; from 9.10 before 9.10.1.17 — fixed in 9.10.1.17, 9.4.4.34, 9.6.4.25, 9.8.4, 9.9.2.50
Cisco Firepower Threat Defense Software: before 6.2.3.12; from 6.3.0 before 6.3.0.3 — fixed in 6.2.3.12, 6.3.0.3

How to fix

Upgrade to a fixed version: Cisco ASA Software 9.10.1.17, 9.4.4.34, 9.6.4.25, 9.8.4; Cisco Firepower Threat Defense Software 6.2.3.12, 6.3.0.3. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2019-1694 or the next vulnerability affects your stack