Advisories

Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software TCP DNS Denial of Service Vulnerability

A vulnerability in the DNS over TCP implementation of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the TCP DNS response handler to unexpectedly restart, causing the device to reload. This vulnerability is due to a logic error when parsing a DNS query and tracking the size of the incoming buffers. An attacker could exploit this vulnerability by formatting a crafted reply to a DNS query sent from the targeted device. A successful exploit could allow the attacker to cause the device to reload, causing a denial of service (DoS) condition. Note: The attacker must be

Read at Cisco PSIRT Security Advisories

Vendor

Cisco

Product

ASA, Firepower / FTD

Fix

available

Exposure class

Edge / VPN / firewall

• Cisco PSIRT Security Advisories (sec.cloudapps.cisco.com)
• CVE-2026-20248 on this site · NVD · CVE.org · Vulnpedia

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