---
title: "CVE-2026-20154: Cisco Secure Firewall ASA & FTD Software - Denial of Service"
description: "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."
url: https://panop.io/threat-heartbeat/CVE-2026-20154/
---

# 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 ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-20154)

## 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](https://cwe.mitre.org/data/definitions/835.html)

## 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

- [https://nvd.nist.gov/vuln/detail/CVE-2026-20154](https://nvd.nist.gov/vuln/detail/CVE-2026-20154)
- [https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-ftd-logging-dos-ZXXNesfN](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-ftd-logging-dos-ZXXNesfN)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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