High8.6Cisco

High [CVE-2026-20082] Cisco Secure Firewall Adaptive Security Appliance Software TCP Flood Denial of Service Vulnerability

This high-severity Cisco advisory covers CVE-2026-20082 affecting Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.20.4.14, FTD, FMC.

cisco-sa-asa-dos-FCvLD6vR Published Mar 4, 2026Updated by vendor Mar 4, 2026

CVE-2026-20082

Affected products & platforms

CiscoFirewallASA / Firepower

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Summary

A vulnerability in the handling of the embryonic connection limits in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software could allow an unauthenticated, remote attacker to cause incoming TCP SYN packets to be dropped incorrectly.

This vulnerability is due to improper handling of new, incoming TCP connections that are destined to management or data interfaces when the device is under a TCP SYN flood attack. An attacker could exploit this vulnerability by sending a crafted stream of traffic to an affected device.

A successful exploit could allow the attacker to prevent all incom…

Affected products named by the advisory: Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.20.4.14; FTD; FMC.

Affected versions

Scope: This vulnerability affects only Cisco Secure Firewall ASA Software Release 9.20.4.14, regardless of device configuration. The fixed software release for this vulnerability is Cisco Secure Firewall ASA Software Release 9.20.4.19.
Release 9.20.4.14 (first fixed: 9.20.4.19)

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Fixed versions

9.20.4.19

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Mitigation checklist

Recommended fix / mitigation

Upgrade to the first fixed release for your train per the Fixed Releases table in this advisory.
Release 9.20.4.14: upgrade to 9.20.4.19.

Workaround status

There are no workarounds that address this vulnerability.

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Sources

Official and corroborating records used to build this advisory.

Cisco Security Advisories (PSIRT)official
Official vendor feed — the source of truth for this advisory. VulniPulse polled this feed and parsed this entry from it. Discovered from the machine-readable feed https://sec.cloudapps.cisco.com/security/center/psirtrss20/CiscoSecurityAdvisory.xml; this link opens the Cisco advisory index instead of the raw feed document.
Cisco
Vendor advisory pageofficial
Advisory page fetched and parsed to extract affected/fixed versions and mitigation guidance beyond what the feed carries.
Cisco

Cross-references

Validate CVE metadata against the authoritative registries.

CVE-2026-20082NVD CVE.org MITRE

Official resources

Cisco ASA upgrade guide (target: 9.20.4.19)
Official documentation
This advisory names 9.20.4.19 as the first fixed release — official upgrade documentation for Cisco ASA (Adaptive Security Appliance) software.
Cisco Secure Firewall Threat Defense (FTD) upgrade guide (target: 9.20.4.19)
Official documentation
This advisory names 9.20.4.19 as the first fixed release — official upgrade documentation for Cisco Secure Firewall Threat Defense (FTD) and FMC.
Cisco Secure Firewall compatibility & release notes
Release notes
Confirm FTD/FMC version compatibility before upgrading.
Cisco Software Checker
Official documentation
Official tool to confirm whether your exact IOS / IOS XE / NX-OS / ASA / FTD / SD-WAN release is affected and to find the first fixed release.

Discussion(0)

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