// For flags

CVE-2021-27854

L2 network filtering bypass using stacked VLAN0, LLC/SNAP headers, and Ethernet to Wifi frame translation

Severity Score

4.7
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

Track
*SSVC
Descriptions

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.

Las capacidades de filtrado de red de capa 2, como la protección RA de IPv6, pueden omitirse usando combinaciones de encabezados VLAN 0, encabezados LLC/SNAP y convirtiendo tramas de Ethernet a Wifi y su inversa

*Credits: Etienne Champetier (@champtar) <champetier.etienne@gmail.com>
CVSS Scores
Attack Vector
Adjacent
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
None
Integrity
Low
Availability
None
Attack Vector
Adjacent
Attack Complexity
Low
Authentication
None
Confidentiality
None
Integrity
Partial
Availability
None
* Common Vulnerability Scoring System
SSVC
  • Decision:Track
Exploitation
None
Automatable
No
Tech. Impact
Partial
* Organization's Worst-case Scenario
Timeline
  • 2021-03-01 CVE Reserved
  • 2022-09-27 CVE Published
  • 2025-05-21 CVE Updated
  • 2025-06-22 EPSS Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-290: Authentication Bypass by Spoofing
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Ieee
Search vendor "Ieee"
 Ieee 802.2
Search vendor "Ieee" for product "Ieee 802.2"
 <= 802.2h-1997
Search vendor "Ieee" for product "Ieee 802.2" and version " <= 802.2h-1997"
-
Affected
Ietf
Search vendor "Ietf"
 P802.1q
Search vendor "Ietf" for product "P802.1q"
 <= d1.0
Search vendor "Ietf" for product "P802.1q" and version " <= d1.0"
-
Affected