Answer in brief
CVE-2026-20248 records a Medium severity (CVSS 6.8) vulnerability in Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software TCP DNS Denial of Service Vulnerability. The current sources do not mark it as known exploited. The current feed maps Cisco/Cisco Secure Firewall Adaptive Security Appliance (ASA) Software (generic), Cisco/Cisco Secure Firewall Threat Defense (FTD) Software (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 6.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Cisco/Cisco Secure Firewall Adaptive Security Appliance (ASA) Software (generic), Cisco/Cisco Secure Firewall Threat Defense (FTD) Software (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Cisco/Cisco Secure Firewall Adaptive Security Appliance (ASA) Softwaregeneric | 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 | Not reported |
| Cisco/Cisco Secure Firewall Threat Defense (FTD) Softwaregeneric | 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 | Not reported |
Published upstream
Sep 16, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 18, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 16, 2026
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.
Quoted source text, attributed separately from HOL analysis.