# CVE-2026-20173: Cisco NX-OS Software Denial of Service Vulnerability

> An unauthenticated remote attacker can cause a denial of service by sending high-rate UDP or TCP traffic to data plane interfaces, exhausting system resources.

- **Severity:** Medium 5.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 7 Oct 2026
- **Updated:** 7 Oct 2026
- **Also known as:** GHSA-8g9j-7mq6-rw6g

## What is CVE-2026-20173?

CVE-2026-20173 is a medium-severity denial of service vulnerability in Cisco NX-OS Software, published on 7 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in Cisco NX-OS Software could allow an unauthenticated, remote attacker to exhaust system resources, causing a denial of service (DoS) condition.

This vulnerability exists because rate limiting was improperly applied to some protocols. An attacker could exploit this vulnerability by sending a high rate of UDP or TCP connections to a data plane interface on an affected device. A successful exploit could allow the attacker to cause instability to various routing and control plane protocols through some packet loss and temporary disruptions, causing a DoS condition. This DoS condition will clear without manual intervention soon after the high rate of traffic is stopped.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-20173?


## How do I fix CVE-2026-20173?

No fix has been published for CVE-2026-20173 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-20173 being exploited?

There is no known exploitation of CVE-2026-20173 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-20173 and fix it if it is affected.

What it is: CVE-2026-20173 is a medium-severity denial of service vulnerability in Cisco NX-OS Software, published on 7 Oct 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-2026-20173 in the wild and no public exploit code.

Affected product: Cisco NX-OS 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-2026-20173/ (Markdown: https://insights.sbomify.com/CVE-2026-20173/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-20173
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-20173
- OSV: https://osv.dev/vulnerability/CVE-2026-20173

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-20173/
Summaries are generated and may contain mistakes; the official description above is the record.