# CVE-2026-20154: Denial of service in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software

> Remote attackers can cause denial of service on Cisco ASA and FTD devices by flooding SYN packets, leading to high CPU utilization.

- **Severity:** High 8.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Sep 2026
- **Updated:** 18 Sep 2026
- **Also known as:** GHSA-fcpc-64j2-96jc

## What is CVE-2026-20154?

CVE-2026-20154 is a high-severity denial of service vulnerability in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the system rate-limiting process for syslog message 419002 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 high CPU utilization on an affected device, resulting in a denial of service (DoS) condition.

This vulnerability is due to improper rate limiting for syslog message 419002. An attacker could exploit this vulnerability by sending a flood of TCP synchronization (SYN) packets to an affected device. A successful exploit could allow the attacker to cause high CPU utilization, resulting in performance degradation. 

Weakness: CWE-835 (Loop with Unreachable Exit Condition)

## Which versions are affected by CVE-2026-20154?


## How do I fix CVE-2026-20154?

No fix has been published for CVE-2026-20154 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-20154 being exploited?

There is no known exploitation of CVE-2026-20154 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-20154 and fix it if it is affected.

What it is: CVE-2026-20154 is a high-severity denial of service vulnerability in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-20154 in the wild and no public exploit code.

Affected product: Cisco Secure Firewall Adaptive Security Appliance (ASA) Software. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-20154/ (Markdown: https://insights.sbomify.com/CVE-2026-20154/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-20154
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-20154
- OSV: https://osv.dev/vulnerability/CVE-2026-20154

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-20154/
Summaries are generated and may contain mistakes; the official description above is the record.