Cisco IOS/IOS XE/Meraki/NX-OS/Small Business Switch IPv6 RA Guard access control

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-$5k0.00

Summaryinfo

A vulnerability was found in Cisco IOS, IOS XE, Meraki, NX-OS and Small Business Switch. It has been declared as critical. The impacted element is an unknown function of the component IPv6 RA Guard. Executing a manipulation can lead to access control. This vulnerability is handled as CVE-2021-27861. The attack can only be done within the local network. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Cisco IOS, IOS XE, Meraki, NX-OS and Small Business Switch (Router Operating System). This vulnerability affects some unknown processing of the component IPv6 RA Guard. The manipulation with an unknown input leads to a access control vulnerability. The CWE definition for the vulnerability is CWE-284. The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)

The weakness was released 09/28/2022 as cisco-sa-VU855201-J3z8CKTX. The advisory is shared for download at tools.cisco.com. This vulnerability was named CVE-2021-27861 since 03/01/2021. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 05/21/2025). The MITRE ATT&CK project declares the attack technique as T1068.

Upgrading eliminates this vulnerability.

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Type

Vendor

Name

License

Website

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

AVACAuCIA
💳💳💳💳💳💳
💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock

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

Exploitinginfo

Class: Access control
CWE: CWE-284 / CWE-266
CAPEC: 🔍
ATT&CK: 🔍

Physical: No
Local: No
Remote: Partially

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-DayUnlockUnlockUnlockUnlock
TodayUnlockUnlockUnlockUnlock

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-2021-27861 (🔍)
GCVE (CVE): GCVE-0-2021-27861
GCVE (VulDB): GCVE-100-209656
scip Labs: https://www.scip.ch/en/?labs.20150108

Entryinfo

Created: 09/28/2022 07:05
Updated: 05/21/2025 20:03
Changes: 09/28/2022 07:05 (40), 10/24/2022 15:41 (11), 05/21/2025 20:03 (15)
Complete: 🔍
Cache ID: 216::103

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Discussion

No comments yet. Languages: en.

Please log in to comment.

◂ PreviousOverviewNext ▸

Interested in the pricing of exploits?

See the underground prices here!