CVE-2026-20154 Cisco Secure Firewall ASA & FTD Software - Denial of Service

Cisco Secure Firewall ASA and FTD Software contain a denial of service vulnerability caused by improper rate limiting of syslog message 419002, letting unauthenticated remote attackers cause high CPU utilization via TCP SYN flood.

CVSS base score 8.6 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.40% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Denial of Service
Impact
Denial Of Service
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Published
16 September 2026
Updated
15 October 2026
Weakness
CWE-835

Vendor fix

Update to the latest available version that addresses the rate-limiting issue.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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