CVE-2026-20248
MEDIUMDescription
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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
Exploit Intelligence
EPSS data unavailable for this CVE.
References
Related Vulnerabilities
Other CWE-195 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2022-43663 | High | 8.1 | 14% | - | - |
| CVE-2020-6096 | High | 8.1 | 5.4% | - | Fix |
| CVE-2011-3045 | High | 8.8 | 3.6% | - | Fix |
| CVE-2016-6560 | High | 8.6 | 1.7% | - | - |
| CVE-2023-3635 | Medium | 5.9 | 1.3% | - | Fix |
| CVE-2020-1913 | High | 8.1 | 1.2% | - | - |
Common questions
How do I fix CVE-2026-20248?
No published fix for CVE-2026-20248 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
How severe is CVE-2026-20248?
CVE-2026-20248 has a CVSS v3 base score of 6.8, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-09-18.