CVE-2021-34778

LLDP database corruption via missing length checks

Published Oct 6, 2021 · Updated Nov 7, 2024

Memory corruption in Cisco Small Business 200 Series Smart Switches allows unauthenticated adjacent attackers to corrupt LLDP data. Missing length validation while processing LLDP messages permits an out-of-bounds read of packet data that corrupts the internal LLDP database. Exploitation requires presence in the same Layer 2 broadcast domain; Cisco reports integrity impact without public malicious use.

CVSS severity4.3
Medium
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in Cisco Small Business 200 Series Smart Switches allows unauthenticated adjacent attackers to corrupt LLDP data. Missing length validation while processing LLDP messages permits an out-of-bounds read of packet data that corrupts the internal LLDP database. Exploitation requires presence in the same Layer 2 broadcast domain; Cisco reports integrity impact without public malicious use.

The record

CVE
CVE-2021-34778
Published
Oct 6, 2021
Updated
Nov 7, 2024
Vendor
ClamAV
Product
Cisco Small Business 200 Series Smart Switches
Classifications
CWE-125, CWE-120, T1210
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 7, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Small Business 200 Series Smart Switchesversion=n/a

Published CVSS scores

4.3CiscoCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
CWE-120Classic Buffer Overflow
T1210Exploitation of Remote Services

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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