CVE-2019-1738: Cisco IOS

High severity, CVSS 7.5. EPSS: 2.5% chance of exploitation in the next 30 days.

A vulnerability in the Network-Based Application Recognition (NBAR) feature of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload. This vulnerability is due to a parsing issue on DNS packets. An attacker could exploit these vulnerabilities by sending crafted DNS packets through routers that are running an affected version and have NBAR enabled. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition.

Affected products

• Cisco IOS: version 15.1(2)sg8a only; version 15.1(3)svg3d only; version 15.1(3)svi1b only; version 15.1(3)svk4b only; version 15.1(3)svk4c only; version 15.1(3)svm3 only; …
• Cisco IOS XE: version 3.2.0ja only; version 3.16.0as only; version 3.16.0bs only; version 3.16.0cs only; version 3.16.0s only; version 3.16.1as only; …

Published 2019-03-28. Last modified 2026-06-17.