VDB-209655 · CVE-2021-27854 · GCVE-0-2021-27854

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

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
5.4	$0-$5k	0.00

Summaryinfo

A vulnerability was found in Cisco IOS, IOS XE, Meraki, NX-OS and Small Business Switch. It has been classified as critical. The affected element is an unknown function of the component IPv6 RA Guard. Performing a manipulation results in authentication spoofing. This vulnerability is known as CVE-2021-27854. Access to the local network is required for this attack. No exploit is available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as critical has been found in Cisco IOS, IOS XE, Meraki, NX-OS and Small Business Switch (Router Operating System). This affects an unknown code block of the component IPv6 RA Guard. The manipulation with an unknown input leads to a authentication spoofing vulnerability. CWE is classifying the issue as CWE-290. This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using combinations of VLAN 0 headers, LLC/SNAP headers, and converting frames from Ethernet to Wifi and its reverse.

The weakness was published 09/28/2022 as cisco-sa-VU855201-J3z8CKTX. It is possible to read the advisory at tools.cisco.com. This vulnerability is uniquely identified as CVE-2021-27854 since 03/01/2021. The technical details are unknown and an exploit is not publicly available.

Upgrading eliminates this vulnerability.

Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

Router Operating System

Vendor

Cisco

Name

License

commercial

Website

Vendor: https://www.cisco.com/

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

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: 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

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

Exploitinginfo

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

Physical: No
Local: No
Remote: Partially

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔍

Timelineinfo

03/01/2021 🔍
09/28/2022 +575 days 🔍
09/28/2022 +0 days 🔍
05/21/2025 +966 days 🔍

Sourcesinfo

Vendor: cisco.com

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

CVE: CVE-2021-27854 (🔍)
GCVE (CVE): GCVE-0-2021-27854
GCVE (VulDB): GCVE-100-209655
scip Labs: https://www.scip.ch/en/?labs.20150108

Entryinfo

Created: 09/28/2022 07:04
Updated: 05/21/2025 20:03
Changes: 09/28/2022 07:04 (40), 10/24/2022 15:35 (11), 05/21/2025 20:03 (15)
Complete: 🔍
Cache ID: 216::103