# CVE-2020-3231: Auth bypass in Cisco IOS 15.2(5a)E

> An unauthenticated adjacent attacker can bypass 802.1X authentication to send and receive broadcast traffic on Cisco Catalyst switches.

- **Severity:** Medium 4.7 (`CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:L/I:N/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:** 3 Jun 2020
- **Updated:** 15 Nov 2024
- **Also known as:** GHSA-q4w2-p3xv-w8vf

## What is CVE-2020-3231?

CVE-2020-3231 is a medium-severity authentication bypass vulnerability in Cisco Ios, published on 3 Jun 2020. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability in the 802.1X feature of Cisco Catalyst 2960-L Series Switches and Cisco Catalyst CDB-8P Switches could allow an unauthenticated, adjacent attacker to forward broadcast traffic before being authenticated on the port. The vulnerability exists because broadcast traffic that is received on the 802.1X-enabled port is mishandled. An attacker could exploit this vulnerability by sending broadcast traffic on the port before being authenticated. A successful exploit could allow the attacker to send and receive broadcast traffic on the 802.1X-enabled port before authentication.

Weakness: CWE-863 (Incorrect Authorization), CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2020-3231?

It affects 1 product.


Products: Cisco Ios.

## How do I fix CVE-2020-3231?

No fix has been published for CVE-2020-3231 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-3231 being exploited?

There is no known exploitation of CVE-2020-3231 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Ios

- [CVE-2017-12240](https://insights.sbomify.com/CVE-2017-12240/): Cisco IOS and IOS XE Software DHCP Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2017-3881](https://insights.sbomify.com/CVE-2017-3881/): Cisco IOS and IOS XE Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2018-0167](https://insights.sbomify.com/CVE-2018-0167/): Cisco IOS, XR, and XE Software Buffer Overflow (high 8.8, exploited in the wild)
- [CVE-2017-6736](https://insights.sbomify.com/CVE-2017-6736/): Cisco IOS and IOS XE Software SNMP Remote Code Execution (high 8.8, exploited in the wild)
- [CVE-2017-6737](https://insights.sbomify.com/CVE-2017-6737/): Cisco IOS and IOS XE Software SNMP Remote Code Execution (high 8.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-3231 and fix it if it is affected.

What it is: CVE-2020-3231 is a medium-severity authentication bypass vulnerability in Cisco Ios, published on 3 Jun 2020. 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-2020-3231 in the wild and no public exploit code.

Affected product: Cisco Ios. 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-2020-3231/ (Markdown: https://insights.sbomify.com/CVE-2020-3231/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-3231
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-3231
- OSV: https://osv.dev/vulnerability/CVE-2020-3231

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-3231/
Summaries are generated and may contain mistakes; the official description above is the record.