// For flags

CVE-2021-27861

L2 network filtering bypass using stacked VLAN0 and LLC/SNAP headers with invalid lengths

Severity Score

4.7
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

-
*SSVC
Descriptions

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

Las capacidades de filtrado de red de capa 2, como la protección RA de IPv6, pueden omitirse usando encabezados LLC/SNAP con una longitud no válida (y, opcionalmente, encabezados VLAN0)

*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:-
Exploitation
-
Automatable
-
Tech. Impact
-
* Organization's Worst-case Scenario
Timeline
  • 2021-03-01 CVE Reserved
  • 2022-09-27 CVE Published
  • 2024-09-16 CVE Updated
  • 2025-03-30 EPSS Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-130: Improper Handling of Length Parameter Inconsistency
  • 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