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.

No CVSS v4.0

Attack Vector Network

Attack Complexity High

Privileges Required None

Scope Changed

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

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

No data.

No data.

No data.

Project Subscriptions

No data.

Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-tcpdns-dos-p6dUnjr5 cve-icon cve-icon
History

Wed, 16 Sep 2026 20:30:00 +0000

Type Values Removed Values Added
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.
Title Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software TCP DNS Denial of Service Vulnerability
Weaknesses CWE-195
References
Metrics cvssV3_1

{'score': 6.8, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: cisco

Published:

Updated: 2026-09-16T20:17:47.838Z

Reserved: 2025-10-08T11:59:15.401Z

Link: CVE-2026-20248

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-16T21:17:08.320

Modified: 2026-09-16T21:17:08.320

Link: CVE-2026-20248

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses