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CVE-2021-34703

Cisco IOS and IOS XE Software Link Layer Discovery Protocol Denial of Service Vulnerability

MEDIUM
6.5
CVSS Score
Published: September 23, 2021 at 02:25 AM UTC
Updated: June 17, 2026 at 03:56 AM UTC
203 products affected across 1 vendorIOSIOS XeCatalyst 9800-L

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Severity
MEDIUM6.5
Exploit prediction
EPSS 1%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

IOS· Cisconpm
95%
v ≤ 16.12.3
cisco-1000-integrated-services-router (environment) · cisco-1100-4g-6g-integrated-services-router (environment) · cisco-1100-4p-integrated-services-router (environment) · cisco-1100-8p-integrated-services-router (environment) · cisco-1100-integrated-services-router (environment) · cisco-1101-4p-integrated-services-router (environment) · cisco-1101-integrated-services-router (environment) · cisco-1109-2p-integrated-services-router (environment) · cisco-1109-4p-integrated-services-router (environment) · cisco-1109-integrated-services-router (environment) · cisco-1111x-8p-integrated-services-router (environment) · cisco-1111x-integrated-services-router (environment) · cisco-111x-integrated-services-router (environment) · cisco-1120-integrated-services-router (environment) · cisco-1160-integrated-services-router (environment) · cisco-4000-integrated-services-router (environment) · cisco-4221-integrated-services-router (environment) · cisco-4321-integrated-services-router (environment) · cisco-4331-integrated-services-router (environment) · cisco-4351-integrated-services-router (environment) · cisco-4431-integrated-services-router (environment) · cisco-4451-integrated-services-router (environment) · cisco-4451-x-integrated-services-router (environment) · cisco-4461-integrated-services-router (environment) · cisco-catalyst-3650-12x48fd-e (environment) · cisco-catalyst-3650-12x48fd-l (environment) · cisco-catalyst-3650-12x48fd-s (environment) · cisco-catalyst-3650-12x48uq (environment) · cisco-catalyst-3650-12x48uq-e (environment) · cisco-catalyst-3650-12x48uq-l (environment) · cisco-catalyst-3650-12x48uq-s (environment) · cisco-catalyst-3650-12x48ur (environment) · cisco-catalyst-3650-12x48ur-e (environment) · cisco-catalyst-3650-12x48ur-l (environment) · cisco-catalyst-3650-12x48ur-s (environment) · cisco-catalyst-3650-12x48uz (environment) · cisco-catalyst-3650-12x48uz-e (environment) · cisco-catalyst-3650-12x48uz-l (environment) · cisco-catalyst-3650-12x48uz-s (environment) · cisco-catalyst-3650-24pd (environment) · cisco-catalyst-3650-24pd-e (environment) · cisco-catalyst-3650-24pd-l (environment) · cisco-catalyst-3650-24pd-s (environment) · cisco-catalyst-3650-24pdm (environment) · cisco-catalyst-3650-24pdm-e (environment) · cisco-catalyst-3650-24pdm-l (environment) · cisco-catalyst-3650-24pdm-s (environment) · cisco-catalyst-3650-24ps-e (environment) · cisco-catalyst-3650-24ps-l (environment) · cisco-catalyst-3650-24ps-s (environment) · cisco-catalyst-3650-24td-e (environment) · cisco-catalyst-3650-24td-l (environment) · cisco-catalyst-3650-24td-s (environment) · cisco-catalyst-3650-24ts-e (environment) · cisco-catalyst-3650-24ts-l (environment) · cisco-catalyst-3650-24ts-s (environment) · cisco-catalyst-3650-48fd-e (environment) · cisco-catalyst-3650-48fd-l (environment) · cisco-catalyst-3650-48fd-s (environment) · cisco-catalyst-3650-48fq (environment) · cisco-catalyst-3650-48fq-e (environment) · cisco-catalyst-3650-48fq-l (environment) · cisco-catalyst-3650-48fq-s (environment) · cisco-catalyst-3650-48fqm (environment) · cisco-catalyst-3650-48fqm-e (environment) · cisco-catalyst-3650-48fqm-l (environment) · cisco-catalyst-3650-48fqm-s (environment) · cisco-catalyst-3650-48fs-e (environment) · cisco-catalyst-3650-48fs-l (environment) · cisco-catalyst-3650-48fs-s (environment) · cisco-catalyst-3650-48pd-e (environment) · cisco-catalyst-3650-48pd-l (environment) · cisco-catalyst-3650-48pd-s (environment) · cisco-catalyst-3650-48pq-e (environment) · cisco-catalyst-3650-48pq-l (environment) · cisco-catalyst-3650-48pq-s (environment) · cisco-catalyst-3650-48ps-e (environment) · cisco-catalyst-3650-48ps-l (environment) · cisco-catalyst-3650-48ps-s (environment) · cisco-catalyst-3650-48td-e (environment) · cisco-catalyst-3650-48td-l (environment) · cisco-catalyst-3650-48td-s (environment) · cisco-catalyst-3650-48tq-e (environment) · cisco-catalyst-3650-48tq-l (environment) · cisco-catalyst-3650-48tq-s (environment) · cisco-catalyst-3650-48ts-e (environment) · cisco-catalyst-3650-48ts-l (environment) · cisco-catalyst-3650-48ts-s (environment) · cisco-catalyst-3650-8x24pd-e (environment) · cisco-catalyst-3650-8x24pd-l (environment) · cisco-catalyst-3650-8x24pd-s (environment) · cisco-catalyst-3650-8x24uq (environment) · cisco-catalyst-3650-8x24uq-e (environment) · cisco-catalyst-3650-8x24uq-l (environment) · cisco-catalyst-3650-8x24uq-s (environment) · cisco-catalyst-3850 (environment) · cisco-catalyst-3850-12s-e (environment) · cisco-catalyst-3850-12s-s (environment) · cisco-catalyst-3850-12x48u (environment) · cisco-catalyst-3850-12xs-e (environment) · cisco-catalyst-3850-12xs-s (environment) · cisco-catalyst-3850-16xs-e (environment) · cisco-catalyst-3850-16xs-s (environment) · cisco-catalyst-3850-24p-e (environment) · cisco-catalyst-3850-24p-l (environment) · cisco-catalyst-3850-24p-s (environment) · cisco-catalyst-3850-24pw-s (environment) · cisco-catalyst-3850-24s-e (environment) · cisco-catalyst-3850-24s-s (environment) · cisco-catalyst-3850-24t-e (environment) · cisco-catalyst-3850-24t-l (environment) · cisco-catalyst-3850-24t-s (environment) · cisco-catalyst-3850-24u (environment) · cisco-catalyst-3850-24u-e (environment) · cisco-catalyst-3850-24u-l (environment) · cisco-catalyst-3850-24u-s (environment) · cisco-catalyst-3850-24xs (environment) · cisco-catalyst-3850-24xs-e (environment) · cisco-catalyst-3850-24xs-s (environment) · cisco-catalyst-3850-24xu (environment) · cisco-catalyst-3850-24xu-e (environment) · cisco-catalyst-3850-24xu-l (environment) · cisco-catalyst-3850-24xu-s (environment) · cisco-catalyst-3850-32xs-e (environment) · cisco-catalyst-3850-32xs-s (environment) · cisco-catalyst-3850-48f-e (environment) · cisco-catalyst-3850-48f-l (environment) · cisco-catalyst-3850-48f-s (environment) · cisco-catalyst-3850-48p-e (environment) · cisco-catalyst-3850-48p-l (environment) · cisco-catalyst-3850-48p-s (environment) · cisco-catalyst-3850-48pw-s (environment) · cisco-catalyst-3850-48t-e (environment) · cisco-catalyst-3850-48t-l (environment) · cisco-catalyst-3850-48t-s (environment) · cisco-catalyst-3850-48u (environment) · cisco-catalyst-3850-48u-e (environment) · cisco-catalyst-3850-48u-l (environment) · cisco-catalyst-3850-48u-s (environment) · cisco-catalyst-3850-48xs (environment) · cisco-catalyst-3850-48xs-e (environment) · cisco-catalyst-3850-48xs-f-e (environment) · cisco-catalyst-3850-48xs-f-s (environment) · cisco-catalyst-3850-48xs-s (environment) · cisco-catalyst-3850-nm-2-40g (environment) · cisco-catalyst-3850-nm-8-10g (environment) · cisco-catalyst-9200 (environment) · cisco-catalyst-9300 (environment) · cisco-catalyst-9300-24p-a (environment) · cisco-catalyst-9300-24p-e (environment) · cisco-catalyst-9300-24s-a (environment) · cisco-catalyst-9300-24s-e (environment) · cisco-catalyst-9300-24t-a (environment) · cisco-catalyst-9300-24t-e (environment) · cisco-catalyst-9300-24u-a (environment) · cisco-catalyst-9300-24u-e (environment) · cisco-catalyst-9300-24ux-a (environment) · cisco-catalyst-9300-24ux-e (environment) · cisco-catalyst-9300-48p-a (environment) · cisco-catalyst-9300-48p-e (environment) · cisco-catalyst-9300-48s-a (environment) · cisco-catalyst-9300-48s-e (environment) · cisco-catalyst-9300-48t-a (environment) · cisco-catalyst-9300-48t-e (environment) · cisco-catalyst-9300-48u-a (environment) · cisco-catalyst-9300-48u-e (environment) · cisco-catalyst-9300-48un-a (environment) · cisco-catalyst-9300-48un-e (environment) · cisco-catalyst-9300-48uxm-a (environment) · cisco-catalyst-9300-48uxm-e (environment) · cisco-catalyst-9300l (environment) · cisco-catalyst-9300l-24p-4g-a (environment) · cisco-catalyst-9300l-24p-4g-e (environment) · cisco-catalyst-9300l-24p-4x-a (environment) · cisco-catalyst-9300l-24p-4x-e (environment) · cisco-catalyst-9300l-24t-4g-a (environment) · cisco-catalyst-9300l-24t-4g-e (environment) · cisco-catalyst-9300l-24t-4x-a (environment) · cisco-catalyst-9300l-24t-4x-e (environment) · cisco-catalyst-9300l-48p-4g-a (environment) · cisco-catalyst-9300l-48p-4g-e (environment) · cisco-catalyst-9300l-48p-4x-a (environment) · cisco-catalyst-9300l-48p-4x-e (environment) · cisco-catalyst-9300l-48t-4g-a (environment) · cisco-catalyst-9300l-48t-4g-e (environment) · cisco-catalyst-9300l-48t-4x-a (environment) · cisco-catalyst-9300l-48t-4x-e (environment) · cisco-catalyst-9300l-stack (environment) · cisco-catalyst-9400 (environment) · cisco-catalyst-9407r (environment) · cisco-catalyst-9410r (environment) · cisco-catalyst-9500 (environment) · cisco-catalyst-9600 (environment) · cisco-catalyst-9800 (environment) · cisco-catalyst-9800-40 (environment) · cisco-catalyst-9800-80 (environment) · cisco-catalyst-9800-cl (environment) · cisco-catalyst-9800-l (environment) · cisco-catalyst-9800-l-c (environment) · cisco-catalyst-9800-l-f (environment) · cisco-csr-1000v (environment)
IOS Xe· Cisco
95%
v ≤ 16.12.3
cisco-1000-integrated-services-router (environment) · cisco-1100-4g-6g-integrated-services-router (environment) · cisco-1100-4p-integrated-services-router (environment) · cisco-1100-8p-integrated-services-router (environment) · cisco-1100-integrated-services-router (environment) · cisco-1101-4p-integrated-services-router (environment) · cisco-1101-integrated-services-router (environment) · cisco-1109-2p-integrated-services-router (environment) · cisco-1109-4p-integrated-services-router (environment) · cisco-1109-integrated-services-router (environment) · cisco-1111x-8p-integrated-services-router (environment) · cisco-1111x-integrated-services-router (environment) · cisco-111x-integrated-services-router (environment) · cisco-1120-integrated-services-router (environment) · cisco-1160-integrated-services-router (environment) · cisco-4000-integrated-services-router (environment) · cisco-4221-integrated-services-router (environment) · cisco-4321-integrated-services-router (environment) · cisco-4331-integrated-services-router (environment) · cisco-4351-integrated-services-router (environment) · cisco-4431-integrated-services-router (environment) · cisco-4451-integrated-services-router (environment) · cisco-4451-x-integrated-services-router (environment) · cisco-4461-integrated-services-router (environment) · cisco-catalyst-3650-12x48fd-e (environment) · cisco-catalyst-3650-12x48fd-l (environment) · cisco-catalyst-3650-12x48fd-s (environment) · cisco-catalyst-3650-12x48uq (environment) · cisco-catalyst-3650-12x48uq-e (environment) · cisco-catalyst-3650-12x48uq-l (environment) · cisco-catalyst-3650-12x48uq-s (environment) · cisco-catalyst-3650-12x48ur (environment) · cisco-catalyst-3650-12x48ur-e (environment) · cisco-catalyst-3650-12x48ur-l (environment) · cisco-catalyst-3650-12x48ur-s (environment) · cisco-catalyst-3650-12x48uz (environment) · cisco-catalyst-3650-12x48uz-e (environment) · cisco-catalyst-3650-12x48uz-l (environment) · cisco-catalyst-3650-12x48uz-s (environment) · cisco-catalyst-3650-24pd (environment) · cisco-catalyst-3650-24pd-e (environment) · cisco-catalyst-3650-24pd-l (environment) · cisco-catalyst-3650-24pd-s (environment) · cisco-catalyst-3650-24pdm (environment) · cisco-catalyst-3650-24pdm-e (environment) · cisco-catalyst-3650-24pdm-l (environment) · cisco-catalyst-3650-24pdm-s (environment) · cisco-catalyst-3650-24ps-e (environment) · cisco-catalyst-3650-24ps-l (environment) · cisco-catalyst-3650-24ps-s (environment) · cisco-catalyst-3650-24td-e (environment) · cisco-catalyst-3650-24td-l (environment) · cisco-catalyst-3650-24td-s (environment) · cisco-catalyst-3650-24ts-e (environment) · cisco-catalyst-3650-24ts-l (environment) · cisco-catalyst-3650-24ts-s (environment) · cisco-catalyst-3650-48fd-e (environment) · cisco-catalyst-3650-48fd-l (environment) · cisco-catalyst-3650-48fd-s (environment) · cisco-catalyst-3650-48fq (environment) · cisco-catalyst-3650-48fq-e (environment) · cisco-catalyst-3650-48fq-l (environment) · cisco-catalyst-3650-48fq-s (environment) · cisco-catalyst-3650-48fqm (environment) · cisco-catalyst-3650-48fqm-e (environment) · cisco-catalyst-3650-48fqm-l (environment) · cisco-catalyst-3650-48fqm-s (environment) · cisco-catalyst-3650-48fs-e (environment) · cisco-catalyst-3650-48fs-l (environment) · cisco-catalyst-3650-48fs-s (environment) · cisco-catalyst-3650-48pd-e (environment) · cisco-catalyst-3650-48pd-l (environment) · cisco-catalyst-3650-48pd-s (environment) · cisco-catalyst-3650-48pq-e (environment) · cisco-catalyst-3650-48pq-l (environment) · cisco-catalyst-3650-48pq-s (environment) · cisco-catalyst-3650-48ps-e (environment) · cisco-catalyst-3650-48ps-l (environment) · cisco-catalyst-3650-48ps-s (environment) · cisco-catalyst-3650-48td-e (environment) · cisco-catalyst-3650-48td-l (environment) · cisco-catalyst-3650-48td-s (environment) · cisco-catalyst-3650-48tq-e (environment) · cisco-catalyst-3650-48tq-l (environment) · cisco-catalyst-3650-48tq-s (environment) · cisco-catalyst-3650-48ts-e (environment) · cisco-catalyst-3650-48ts-l (environment) · cisco-catalyst-3650-48ts-s (environment) · cisco-catalyst-3650-8x24pd-e (environment) · cisco-catalyst-3650-8x24pd-l (environment) · cisco-catalyst-3650-8x24pd-s (environment) · cisco-catalyst-3650-8x24uq (environment) · cisco-catalyst-3650-8x24uq-e (environment) · cisco-catalyst-3650-8x24uq-l (environment) · cisco-catalyst-3650-8x24uq-s (environment) · cisco-catalyst-3850 (environment) · cisco-catalyst-3850-12s-e (environment) · cisco-catalyst-3850-12s-s (environment) · cisco-catalyst-3850-12x48u (environment) · cisco-catalyst-3850-12xs-e (environment) · cisco-catalyst-3850-12xs-s (environment) · cisco-catalyst-3850-16xs-e (environment) · cisco-catalyst-3850-16xs-s (environment) · cisco-catalyst-3850-24p-e (environment) · cisco-catalyst-3850-24p-l (environment) · cisco-catalyst-3850-24p-s (environment) · cisco-catalyst-3850-24pw-s (environment) · cisco-catalyst-3850-24s-e (environment) · cisco-catalyst-3850-24s-s (environment) · cisco-catalyst-3850-24t-e (environment) · cisco-catalyst-3850-24t-l (environment) · cisco-catalyst-3850-24t-s (environment) · cisco-catalyst-3850-24u (environment) · cisco-catalyst-3850-24u-e (environment) · cisco-catalyst-3850-24u-l (environment) · cisco-catalyst-3850-24u-s (environment) · cisco-catalyst-3850-24xs (environment) · cisco-catalyst-3850-24xs-e (environment) · cisco-catalyst-3850-24xs-s (environment) · cisco-catalyst-3850-24xu (environment) · cisco-catalyst-3850-24xu-e (environment) · cisco-catalyst-3850-24xu-l (environment) · cisco-catalyst-3850-24xu-s (environment) · cisco-catalyst-3850-32xs-e (environment) · cisco-catalyst-3850-32xs-s (environment) · cisco-catalyst-3850-48f-e (environment) · cisco-catalyst-3850-48f-l (environment) · cisco-catalyst-3850-48f-s (environment) · cisco-catalyst-3850-48p-e (environment) · cisco-catalyst-3850-48p-l (environment) · cisco-catalyst-3850-48p-s (environment) · cisco-catalyst-3850-48pw-s (environment) · cisco-catalyst-3850-48t-e (environment) · cisco-catalyst-3850-48t-l (environment) · cisco-catalyst-3850-48t-s (environment) · cisco-catalyst-3850-48u (environment) · cisco-catalyst-3850-48u-e (environment) · cisco-catalyst-3850-48u-l (environment) · cisco-catalyst-3850-48u-s (environment) · cisco-catalyst-3850-48xs (environment) · cisco-catalyst-3850-48xs-e (environment) · cisco-catalyst-3850-48xs-f-e (environment) · cisco-catalyst-3850-48xs-f-s (environment) · cisco-catalyst-3850-48xs-s (environment) · cisco-catalyst-3850-nm-2-40g (environment) · cisco-catalyst-3850-nm-8-10g (environment) · cisco-catalyst-9200 (environment) · cisco-catalyst-9300 (environment) · cisco-catalyst-9300-24p-a (environment) · cisco-catalyst-9300-24p-e (environment) · cisco-catalyst-9300-24s-a (environment) · cisco-catalyst-9300-24s-e (environment) · cisco-catalyst-9300-24t-a (environment) · cisco-catalyst-9300-24t-e (environment) · cisco-catalyst-9300-24u-a (environment) · cisco-catalyst-9300-24u-e (environment) · cisco-catalyst-9300-24ux-a (environment) · cisco-catalyst-9300-24ux-e (environment) · cisco-catalyst-9300-48p-a (environment) · cisco-catalyst-9300-48p-e (environment) · cisco-catalyst-9300-48s-a (environment) · cisco-catalyst-9300-48s-e (environment) · cisco-catalyst-9300-48t-a (environment) · cisco-catalyst-9300-48t-e (environment) · cisco-catalyst-9300-48u-a (environment) · cisco-catalyst-9300-48u-e (environment) · cisco-catalyst-9300-48un-a (environment) · cisco-catalyst-9300-48un-e (environment) · cisco-catalyst-9300-48uxm-a (environment) · cisco-catalyst-9300-48uxm-e (environment) · cisco-catalyst-9300l (environment) · cisco-catalyst-9300l-24p-4g-a (environment) · cisco-catalyst-9300l-24p-4g-e (environment) · cisco-catalyst-9300l-24p-4x-a (environment) · cisco-catalyst-9300l-24p-4x-e (environment) · cisco-catalyst-9300l-24t-4g-a (environment) · cisco-catalyst-9300l-24t-4g-e (environment) · cisco-catalyst-9300l-24t-4x-a (environment) · cisco-catalyst-9300l-24t-4x-e (environment) · cisco-catalyst-9300l-48p-4g-a (environment) · cisco-catalyst-9300l-48p-4g-e (environment) · cisco-catalyst-9300l-48p-4x-a (environment) · cisco-catalyst-9300l-48p-4x-e (environment) · cisco-catalyst-9300l-48t-4g-a (environment) · cisco-catalyst-9300l-48t-4g-e (environment) · cisco-catalyst-9300l-48t-4x-a (environment) · cisco-catalyst-9300l-48t-4x-e (environment) · cisco-catalyst-9300l-stack (environment) · cisco-catalyst-9400 (environment) · cisco-catalyst-9407r (environment) · cisco-catalyst-9410r (environment) · cisco-catalyst-9500 (environment) · cisco-catalyst-9600 (environment) · cisco-catalyst-9800 (environment) · cisco-catalyst-9800-40 (environment) · cisco-catalyst-9800-80 (environment) · cisco-catalyst-9800-cl (environment) · cisco-catalyst-9800-l (environment) · cisco-catalyst-9800-l-c (environment) · cisco-catalyst-9800-l-f (environment) · cisco-csr-1000v (environment)
1000 Integrated Services Router· Ciscodevice
80%
All versions
1100-4G/6G Integrated Services Router· Ciscodevice
80%
All versions
1100-4P Integrated Services Router· Ciscodevice
80%
All versions
1100-8P Integrated Services Router· Ciscodevice
80%
All versions
1100 Integrated Services Router· Ciscodevice
80%
All versions
1101-4P Integrated Services Router· Ciscodevice
80%
All versions
1101 Integrated Services Router· Ciscodevice
80%
All versions
1109-2P Integrated Services Router· Ciscodevice
80%
All versions

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (1)

Vendor Advisoryx_refsource_CISCO
Source: [email protected]
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-lldp-dos-sBnuHSjT

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.5MEDIUM[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-456CWE-665

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