Cisco IOS and IOS XE Software Link Layer Discovery Protocol Denial of Service VulnerabilityA 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.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-lldp-dos-sBnuHSjT
This advisory is part of the September 2021 release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: September 2021 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.
Security Impact Rating: Medium
CVE: CVE-2021-34703
Source: Cisco IOS and IOS XE Software Link Layer Discovery Protocol Denial of Service Vulnerability (https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-lldp-dos-sBnuHSjT?vs_f=Cisco%20Security%20Advisory&vs_cat=Security%20Intelligence&vs_type=RSS&vs_p=Cisco%20IOS%20and%20IOS%20XE%20Software%20Link%20Layer%20Discovery%20Protocol%20Denial%20of%20Service%20Vulnerability&vs_k=1)