vulntracker.iovulntracker.io
© 2026 vulntracker.io

CVE-2026-20248

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

MEDIUM
6.8
CVSS Score
Published: September 16, 2026 at 08:17 PM UTC
Updated: September 18, 2026 at 02:30 PM UTC
2 products affected across 1 vendorAdaptive Security ApplianceSecure Firewall Threat Defense

Using Cisco Secure Firewall Adaptive Security Appliance (ASA) Software by Cisco?

Get instant alerts when new vulnerabilities affect Cisco Secure Firewall Adaptive Security Appliance (ASA) Software - before attackers find them.

Real-time alertsTrack your software stackFree plan available
Start FreeSign In
Severity
MEDIUM6.8
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Adaptive Security Appliance· Cisco
60%
9.16.19.16.1.289.16.29.16.2.119.16.2.139.16.2.149.16.2.39.16.2.79.16.39.16.3.149.16.3.159.16.3.199.16.3.239.16.3.39.16.49.16.4.149.16.4.189.16.4.199.16.4.279.16.4.389.16.4.399.16.4.429.16.4.489.16.4.559.16.4.579.16.4.619.16.4.629.16.4.679.16.4.709.16.4.719.16.4.769.16.4.829.16.4.849.16.4.859.16.4.899.16.4.99.16.4.929.18.19.18.1.39.18.29.18.2.59.18.2.79.18.2.89.18.39.18.3.399.18.3.469.18.3.539.18.3.559.18.3.569.18.49.18.4.1359.18.4.229.18.4.249.18.4.299.18.4.349.18.4.409.18.4.479.18.4.59.18.4.509.18.4.529.18.4.539.18.4.579.18.4.669.18.4.679.18.4.689.18.4.719.18.4.769.18.4.89.18.4.829.19.19.19.1.129.19.1.189.19.1.229.19.1.249.19.1.279.19.1.289.19.1.319.19.1.379.19.1.389.19.1.429.19.1.59.19.1.99.20.19.20.1.59.20.29.20.2.109.20.2.219.20.2.229.20.39.20.3.109.20.3.139.20.3.169.20.3.209.20.3.49.20.3.79.20.3.99.20.49.20.4.109.20.4.149.20.4.199.20.4.229.20.4.2359.20.4.289.20.4.309.20.4.349.20.4.79.22.1.19.22.1.29.22.1.39.22.1.69.22.29.22.2.139.22.2.149.22.2.209.22.2.329.22.2.49.22.2.99.22.39.22.3.59.23.19.23.1.139.23.1.199.23.1.1959.23.1.229.23.1.269.23.1.39.23.1.329.23.1.79.24.19.24.1.119.24.1.1559.24.1.59.24.1.9
Secure Firewall Threat Defense· Cisco
60%
10.0.07.0.07.0.0.17.0.17.0.1.17.0.27.0.2.17.0.37.0.47.0.57.0.67.0.6.17.0.6.27.0.6.37.0.77.0.87.0.8.17.0.97.2.07.2.0.17.2.17.2.107.2.10.27.2.117.2.27.2.37.2.47.2.4.17.2.57.2.5.17.2.5.27.2.67.2.77.2.87.2.8.17.2.97.3.07.3.17.3.1.17.3.1.27.4.07.4.17.4.1.17.4.27.4.2.17.4.2.27.4.2.37.4.2.47.4.37.4.47.4.77.6.07.6.17.6.27.6.2.17.6.47.7.07.7.107.7.10.17.7.11

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (1)

Source: cverecord
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-tcpdns-dos-p6dUnjr5

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.8MEDIUMcisco
Attack Vector
NETWORK
Complexity
HIGH
Privileges
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusAWAITING ANALYSIS
CWE
CWE-195

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Create accountSign in
Free plan, no card