🔐 CVE Alert

CVE-2026-20248

MEDIUM 6.8

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

CVSS Score
6.8
EPSS Score
0.0%
EPSS Percentile
0th

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 able to respond to DNS queries from the device, either by controlling the DNS service or through a machine-in-the-middle attack.

CWE CWE-195
Vendor cisco
Product cisco secure firewall adaptive security appliance (asa) software
Ecosystems
Industries
NetworkingTelecommunications
Published Sep 16, 2026
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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

Affected Versions

Cisco / Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
9.16.1 9.16.1.28 9.16.2 9.16.2.3 9.16.2.7 9.16.2.11 9.16.2.13 9.16.2.14 9.16.3.3 9.16.3 9.16.3.14 9.18.1 9.16.3.15 9.18.1.3 9.18.2 9.16.3.19 9.16.3.23 9.18.2.5 9.16.4 9.18.2.7 9.19.1 9.16.4.9 9.18.2.8 9.16.4.14 9.18.3 9.19.1.5 9.16.4.18 9.19.1.9 9.18.3.39 9.16.4.19 9.19.1.12 9.18.3.46 9.16.4.27 9.19.1.18 9.18.3.53 9.18.3.55 9.16.4.38 9.16.4.39 9.18.3.56 9.20.1 9.16.4.42 9.19.1.22 9.18.4 9.20.1.5 9.18.4.5 9.19.1.24 9.16.4.48 9.18.4.8 9.20.2 9.19.1.27 9.16.4.55 9.18.4.22 9.20.2.10 9.16.4.57 9.19.1.28 9.18.4.24 9.20.2.21 9.16.4.61 9.19.1.31 9.18.4.29 9.20.2.22 9.16.4.62 9.18.4.34 9.20.3 9.16.4.67 9.16.4.70 9.18.4.40 9.23.1 9.22.1.1 9.16.4.71 9.20.3.4 9.18.4.47 9.20.3.7 9.19.1.37 9.16.4.76 9.20.3.9 9.19.1.38 9.18.4.50 9.22.1.3 9.20.3.10 9.22.1.2 9.18.4.52 9.20.3.13 9.22.1.6 9.18.4.53 9.16.4.82 9.22.2 9.20.3.16 9.19.1.42 9.18.4.57 9.16.4.84 9.23.1.3 9.20.3.20 9.22.2.4 9.23.1.7 9.20.4 9.22.2.9 9.23.1.13 9.20.4.7 9.22.2.13 9.18.4.66 9.20.4.10 9.23.1.19 9.16.4.85 9.22.2.14 9.18.4.67 9.24.1 9.18.4.68 9.23.1.22 9.20.4.14 9.22.2.20 9.18.4.71 9.20.4.19 9.23.1.26 9.16.4.89 9.22.2.32 9.18.4.76 9.22.3 9.24.1.5 9.20.4.22 9.24.1.9 9.20.4.28 9.22.3.5 9.16.4.92 9.18.4.135 9.23.1.195 9.20.4.30 9.24.1.155 9.23.1.32 9.24.1.11 9.20.4.34 9.18.4.82 9.20.4.235
Cisco / Cisco Secure Firewall Threat Defense (FTD) Software
7.0.0 7.0.0.1 7.0.1 7.0.1.1 7.0.2 7.2.0 7.0.2.1 7.0.3 7.2.0.1 7.0.4 7.2.1 7.0.5 7.3.0 7.2.2 7.2.3 7.3.1 7.2.4 7.0.6 7.2.5 7.2.4.1 7.3.1.1 7.4.0 7.0.6.1 7.2.5.1 7.4.1 7.2.6 7.0.6.2 7.4.1.1 7.2.7 7.2.5.2 7.3.1.2 7.2.8 7.6.0 7.4.2 7.2.8.1 7.0.6.3 7.4.2.1 7.2.9 7.0.7 7.7.0 7.4.2.2 7.2.10 7.6.1 7.4.2.3 7.0.8 7.6.2 7.7.10 7.7.11 7.0.8.1 7.6.2.1 7.7.10.1 7.4.2.4 7.2.10.2 7.4.3 7.6.4 10.0.0 7.4.4 7.0.9 7.2.11 7.4.7

References

NVD ↗ CVE.org ↗ EPSS Data ↗
sec.cloudapps.cisco.com: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-tcpdns-dos-p6dUnjr5