# CVE-2021-34776: Cisco Small Business 220 Series Smart Switches Link Layer Discovery Protocol Vulnerabilities

> An adjacent attacker can execute code or cause a reload on Cisco Small Business Smart Switches via LLDP vulnerabilities.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/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:** 6 Oct 2021
- **Updated:** 7 Nov 2024
- **Also known as:** GHSA-9ph8-cf44-5v83

## What is CVE-2021-34776?

CVE-2021-34776 is a medium-severity memory corruption vulnerability in Cisco Small Business 200 Series Smart Switches, published on 6 Oct 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Multiple vulnerabilities exist in the Link Layer Discovery Protocol (LLDP) implementation for Cisco Small Business 220 Series Smart Switches. An unauthenticated, adjacent attacker could perform the following: Execute code on the affected device or cause it to reload unexpectedly Cause LLDP database corruption on the affected device For more information about these vulnerabilities, see the Details section of this advisory. Note: LLDP is a Layer 2 protocol. To exploit these vulnerabilities, an attacker must be in the same broadcast domain as the affected device (Layer 2 adjacent). Cisco has released firmware updates that address these vulnerabilities.

Weakness: CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2021-34776?

It affects 16 products.


Products: Cisco Business 220-16p-2g Firmware, Cisco Business 220-16t-2g Firmware, Cisco Business 220-24fp-4g Firmware, Cisco Business 220-24fp-4x Firmware, Cisco Business 220-24p-4g Firmware, Cisco Business 220-24p-4x Firmware, Cisco Business 220-24t-4g Firmware, Cisco Business 220-24t-4x Firmware, Cisco Business 220-48fp-4x Firmware, Cisco Business 220-48p-4g Firmware, Cisco Business 220-48p-4x Firmware, Cisco Business 220-48t-4g Firmware, Cisco Business 220-48t-4x Firmware, Cisco Business 220-8fp-E-2g Firmware, Cisco Business 220-8p-E-2g Firmware, Cisco Business 220-8t-E-2g Firmware.

## How do I fix CVE-2021-34776?

No fix has been published for CVE-2021-34776 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-34776 being exploited?

There is no known exploitation of CVE-2021-34776 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Small Business 200 Series Smart Switches

- [CVE-2021-34744](https://insights.sbomify.com/CVE-2021-34744/): Cisco Business 220 Series Smart Switches Static Key and Password Vulnerabilities (medium 4.9)
- [CVE-2021-34757](https://insights.sbomify.com/CVE-2021-34757/): Cisco Business 220 Series Smart Switches Static Key and Password Vulnerabilities (medium 4.9)
- [CVE-2021-34775](https://insights.sbomify.com/CVE-2021-34775/): Cisco Small Business 220 Series Smart Switches Link Layer Discovery Protocol Vulnerabilities (medium 4.3)
- [CVE-2021-34777](https://insights.sbomify.com/CVE-2021-34777/): Cisco Small Business 220 Series Smart Switches Link Layer Discovery Protocol Vulnerabilities (medium 4.3)
- [CVE-2021-34778](https://insights.sbomify.com/CVE-2021-34778/): Cisco Small Business 220 Series Smart Switches Link Layer Discovery Protocol Vulnerabilities (medium 4.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34776 and fix it if it is affected.

What it is: CVE-2021-34776 is a medium-severity memory corruption vulnerability in Cisco Small Business 200 Series Smart Switches, published on 6 Oct 2021. 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-2021-34776 in the wild and no public exploit code.

Affected product: Cisco Small Business 200 Series Smart Switches. 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-2021-34776/ (Markdown: https://insights.sbomify.com/CVE-2021-34776/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34776
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34776
- OSV: https://osv.dev/vulnerability/CVE-2021-34776

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-34776/
Summaries are generated and may contain mistakes; the official description above is the record.