CVE-2021-34703

medium

Description

A vulnerability in the Link Layer Discovery Protocol (LLDP) message parser of Cisco IOS Software and Cisco IOS XE Software could allow an attacker to trigger a reload of an affected device, resulting in a denial of service (DoS) condition. This vulnerability is due to improper initialization of a buffer. An attacker could exploit this vulnerability via any of the following methods: An authenticated, remote attacker could access the LLDP neighbor table via either the CLI or SNMP while the device is in a specific state. An unauthenticated, adjacent attacker could corrupt the LLDP neighbor table by injecting specific LLDP frames into the network and then waiting for an administrator of the device or a network management system (NMS) managing the device to retrieve the LLDP neighbor table of the device via either the CLI or SNMP. An authenticated, adjacent attacker with SNMP read-only credentials or low privileges on the device CLI could corrupt the LLDP neighbor table by injecting specific LLDP frames into the network and then accessing the LLDP neighbor table via either the CLI or SNMP. A successful exploit could allow the attacker to cause the affected device to crash, resulting in a reload of the device.

References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-lldp-dos-sBnuHSjT

Details

Source: Mitre, NVD

Published: 2021-09-23

Updated: 2026-06-17

Risk Information

CVSS v2

Base Score: 6.8

Vector: CVSS2#AV:N/AC:L/Au:S/C:N/I:N/A:C

Severity: Medium

CVSS v3

Base Score: 6.5

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Severity: Medium

EPSS

EPSS: 0.00243