CVE-2026-20248

MEDIUM

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 unauthe...

Affects 0 products across 1 vendor.

CVSS 3.16.8
EPSS0.3%
Percentile25th
PatchUnknown
CVSS Vector — Plain English Remotely exploitable over the network, high complexity, no authentication required, no user interaction needed, can impact systems beyond the vulnerable component, no confidentiality impact, no integrity impact, full availability impact.
CWE Weakness Definitions
CWE-195: CWE-195
◆ AI Analysis — automated analysis, not human-reviewed

A medium severity vulnerability (CVE-2026-20248) affects the target system. 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 r...

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Frequently Asked Questions
What is CVE-2026-20248?
A medium severity vulnerability (CVE-2026-20248) affects the target system. 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 r...
What is the CVSS score for CVE-2026-20248?
CVE-2026-20248 has CVSS 6.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H. EPSS: 0.3%.
Is CVE-2026-20248 actively exploited?
No confirmed active exploitation of CVE-2026-20248 as of 2026-09-25.
How do I remediate CVE-2026-20248?
Apply vendor patches for CVE-2026-20248. Monitor Cisco advisories.
What systems are affected by CVE-2026-20248?
CVE-2026-20248 affects: Cisco.
Vulnerability Details
CVE IDCVE-2026-20248
CVSS VectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
Published2026-09-16
Last Modified2026-09-18
ICS Relevance65%
Weakness (CWE)
CWE-195
SourceNVD
Official 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.

Source: NIST NVD / MITRE CVE Database

Affected Products
VendorProductFixed Version
Cisco — —
Remediation

No patch URL on record. Monitor vendor security advisories directly.

Threat Intelligence
● Threat Intelligence Validated: September 2026 | Threat Age: 11 Days
CISA KEVNot in KEV catalog
Public ExploitNot confirmed
PoC CodeNot confirmed
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