# CVE-2026-20038: Cisco Nexus 9000 Series Fabric Switches in ACI Mode Policy-Based Redirect Endpoint Group Contract Bypass Vulnerability

> Unauthenticated remote attackers can bypass EPG contracts on Cisco Nexus 9000 switches in ACI mode by sending specific UDP packets.

- **Severity:** Medium 5.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N`)
- **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-8r87-mj76-xw8h

## What is CVE-2026-20038?

CVE-2026-20038 is a medium-severity vulnerability in Cisco NX-OS System Software in ACI Mode, 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 the endpoint group (EPG) contract functionality of Cisco Nexus 9000 Series Fabric Switches in ACI Mode could allow an unauthenticated, remote attacker to bypass configured EPG contracts.

This vulnerability is due to an improper control with EPG contracts. An attacker could exploit this vulnerability by sending IPv4 or IPv6 packets using UDP source and destination ports that are assigned to DHCP traffic through an affected device. A successful exploit could allow the attacker to bypass EPG contracts on the affected device.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2026-20038?


## How do I fix CVE-2026-20038?

No fix has been published for CVE-2026-20038 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-20038 being exploited?

There is no known exploitation of CVE-2026-20038 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-20038 and fix it if it is affected.

What it is: CVE-2026-20038 is a medium-severity vulnerability in Cisco NX-OS System Software in ACI Mode, 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-2026-20038 in the wild and no public exploit code.

Affected product: Cisco NX-OS System Software in ACI Mode. 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-2026-20038/ (Markdown: https://insights.sbomify.com/CVE-2026-20038/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-20038
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-20038
- OSV: https://osv.dev/vulnerability/CVE-2026-20038

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-20038/
Summaries are generated and may contain mistakes; the official description above is the record.