# CVE-2026-20084: Denial of service in Cisco IOS XE Software

> An unauthenticated remote attacker can cause a denial of service on Cisco Catalyst switches by sending BOOTP packets that leak across VLANs, 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:** 25 Mar 2026
- **Updated:** 26 Mar 2026
- **Also known as:** GHSA-m8vf-g949-jwr2

## What is CVE-2026-20084?

CVE-2026-20084 is a high-severity denial of service vulnerability in Cisco Ios Xe, published on 25 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the DHCP snooping feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause BOOTP packets to be forwarded between VLANs, resulting in a denial of service (DoS) condition. 

 This vulnerability is due to improper handling of BOOTP packets on Cisco Catalyst 9000 Series Switches. An attacker could exploit this vulnerability by sending BOOTP request packets to an affected device. A successful exploit could allow an attacker to forward BOOTP packets from one VLAN to another, resulting in BOOTP VLAN leakage and potentially leading to high CPU utilization. This makes the device unreachable (either through console or remote management) and unable to forward traffic, resulting in a DoS condition. 

 Note: This vulnerability can be exploited with either unicast or broadcast BOOTP packets.

   There are workarounds that address this vulnerability.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-20084?

It affects 1 product.


Products: Cisco Ios Xe.

## How do I fix CVE-2026-20084?

No fix has been published for CVE-2026-20084 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-20084 being exploited?

There is no known exploitation of CVE-2026-20084 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Ios Xe

- [CVE-2023-20198](https://insights.sbomify.com/CVE-2023-20198/): Cisco IOS XE Web UI Privilege Escalation (critical 10.0, exploited in the wild)
- [CVE-2018-0151](https://insights.sbomify.com/CVE-2018-0151/): Cisco IOS Software and Cisco IOS XE Software Quality of Service Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2023-20273](https://insights.sbomify.com/CVE-2023-20273/): Cisco IOS XE Web UI Command Injection (high 7.2, exploited in the wild)
- [CVE-2025-20188](https://insights.sbomify.com/CVE-2025-20188/): Hardcoded credentials in Cisco IOS XE Software (critical 10.0)
- [CVE-2021-34770](https://insights.sbomify.com/CVE-2021-34770/): Cisco IOS XE Software for Catalyst 9000 Family Wireless Controllers CAPWAP Remote Code Execution Vulnerability (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-20084 and fix it if it is affected.

What it is: CVE-2026-20084 is a high-severity denial of service vulnerability in Cisco Ios Xe, published on 25 Mar 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-2026-20084 in the wild and no public exploit code.

Affected product: Cisco Ios Xe. 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-2026-20084/ (Markdown: https://insights.sbomify.com/CVE-2026-20084/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-20084
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-20084
- OSV: https://osv.dev/vulnerability/CVE-2026-20084

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-20084/
Summaries are generated and may contain mistakes; the official description above is the record.