Vulnerability in Cisco Secure Firewall Adaptive Security Appliance (Asa) Software
CVE-2026-20248
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.005 (39.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 39th percentile — 39.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.001
Affected products
- Cisco Secure Firewall Adaptive Security Appliance (Asa) Software — versions 9.16.1, 9.16.1.28, 9.16.2
- Cisco Secure Firewall Threat Defense (Ftd) Software — versions 10.0.0, 7.0.0, 7.0.0.1
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-20248?
- CVE-2026-20248 is a medium-severity vulnerability in Cisco Secure Firewall Adaptive Security Appliance (Asa) Software, classified under CWE-195. CVSS score: 6.8/10. Published 2026-09-16.
- How severe is CVE-2026-20248?
- Medium severity. CVSS v3 base score is 6.8 out of 10.