# CVE-2026-20104: Security feature bypass in Cisco IOS XE Software

> An attacker with local access or physical presence can bypass boot integrity checks to execute arbitrary code on Cisco Catalyst switches.

- **Severity:** Medium 6.1 (`CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 25 Mar 2026
- **Updated:** 26 Mar 2026
- **Also known as:** GHSA-38h5-57rq-7mj8

## What is CVE-2026-20104?

CVE-2026-20104 is a medium-severity vulnerability in Cisco Ios Xe, published on 25 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability in the bootloader of Cisco IOS XE Software for Cisco Catalyst 9200 Series Switches, Cisco Catalyst ESS9300 Embedded Series Switches, Cisco Catalyst IE9310 and IE9320 Rugged Series Switches, and Cisco IE3500 and IE3505 Rugged Series Switches could allow an authenticated, local attacker with level-15 privileges or an unauthenticated attacker with physical access to an affected device to execute arbitrary code at boot time and break the chain of trust.

 This vulnerability is due to insufficient validation of software at boot time. An attacker could exploit this vulnerability by manipulating the loaded binaries on an affected device to bypass some of the integrity checks that are performed during the boot process. A successful exploit could allow the attacker to execute code that bypasses the requirement to run Cisco-signed images.

 Cisco has assigned this security advisory a Security Impact Rating (SIR) of High rather than Medium as the score indicates because this vulnerability allows an attacker to bypass a major security feature of a device.

Weakness: CWE-124 (Buffer Underwrite)

## Which versions are affected by CVE-2026-20104?

It affects 1 product.


Products: Cisco Ios Xe.

## How do I fix CVE-2026-20104?

No fix has been published for CVE-2026-20104 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-20104 being exploited?

There is no known exploitation of CVE-2026-20104 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-2026-20104 and fix it if it is affected.

What it is: CVE-2026-20104 is a medium-severity vulnerability in Cisco Ios Xe, published on 25 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-20104 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-2026-20104/ (Markdown: https://insights.sbomify.com/CVE-2026-20104/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-20104
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-20104
- OSV: https://osv.dev/vulnerability/CVE-2026-20104

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-20104/
Summaries are generated and may contain mistakes; the official description above is the record.