Cisco IOS/IOS XE/Meraki/NX-OS/Small Business Switch IPv6 RA Guard/ARP Inspection authentication spoofing

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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A vulnerability was found in Cisco IOS, IOS XE, Meraki, NX-OS and Small Business Switch (Router Operating System). It has been rated as critical. Affected by this issue is an unknown code of the component IPv6 RA Guard/ARP Inspection. The manipulation with an unknown input leads to a authentication spoofing vulnerability. Using CWE to declare the problem leads to CWE-290. This attack-focused weakness is caused by improperly implemented authentication schemes that are subject to spoofing attacks. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Layer 2 network filtering capabilities such as IPv6 RA guard or ARP inspection can be bypassed using combinations of VLAN 0 headers and LLC/SNAP headers.

The weakness was shared 09/28/2022 as cisco-sa-VU855201-J3z8CKTX. The advisory is available at This vulnerability is handled as CVE-2021-27853 since 03/01/2021. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 10/24/2022).

Upgrading eliminates this vulnerability.






  • commercial

CPE 2.3info

CPE 2.2info


VulDB Meta Base Score: 5.5
VulDB Meta Temp Score: 5.4

VulDB Base Score: 6.3
VulDB Temp Score: 6.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 4.7
NVD Vector: 🔒



VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍


Class: Authentication spoofing
CWE: CWE-290 / CWE-287
ATT&CK: Unknown

Local: No
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒


Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍


Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒


03/01/2021 CVE reserved
09/28/2022 +575 days Advisory disclosed
09/28/2022 +0 days VulDB entry created
10/24/2022 +26 days VulDB last update



Advisory: cisco-sa-VU855201-J3z8CKTX
Status: Confirmed

CVE: CVE-2021-27853 (🔒)
scip Labs:


Created: 09/28/2022 07:03 AM
Updated: 10/24/2022 03:29 PM
Changes: 09/28/2022 07:03 AM (40), 10/24/2022 03:29 PM (11)
Complete: 🔍


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