CVE-2021-34777

What it is

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.

At a glance

Exploitability

Can be exploited from the same network segment without logging in. Limited direct impact.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-10-06 20:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:56 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.4% in the next 30 days (EPSS).
• Severity: 4.3 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-10-06 20:15 UTC

Last modified

2026-06-17 03:56 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-120 · Classic buffer overflow

Record status

Modified

Affected

• Cisco Business 220-8t-e-2g Firmware ≤ 1.2.0.6
• Cisco Business 220-8p-e-2g Firmware ≤ 1.2.0.6
• Cisco Business 220-8fp-e-2g Firmware ≤ 1.2.0.6
• Cisco Business 220-16t-2g Firmware ≤ 1.2.0.6
• Cisco Business 220-16p-2g Firmware ≤ 1.2.0.6
• Cisco Business 220-24t-4g Firmware ≤ 1.2.0.6
• Cisco Business 220-24p-4g Firmware ≤ 1.2.0.6
• Cisco Business 220-24fp-4g Firmware ≤ 1.2.0.6

Attack profile CVSS 3.1 · 4.3

Attack vector

Adjacent network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

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