CVE-2026-20248: Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software TCP DNS Denial of Service Vulnerability
Cisco · Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
Affected: Cisco Secure Firewall Adaptive Security Appliance (ASA) Software · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 39% of scored CVEs
DescriptionCVE.org
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 products2
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- Cisco · Cisco Secure Firewall Adaptive Security Appliance (ASA) Software9.16.1; 9.16.1.28; 9.16.2; 9.16.2.3; 9.16.2.7; 9.16.2.11 and 127 more
- Cisco · Cisco Secure Firewall Threat Defense (FTD) Software7.0.0; 7.0.0.1; 7.0.1; 7.0.1.1; 7.0.2; 7.2.0 and 54 more
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Unlikely (under 1%). EPSS under 1%, or no score yet.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Vendor
- Cisco
- Published
- September 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-20248 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.