CVE-2021-27853 - CVE House
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Status published Unknown CVE-2021-27853

L2 network filtering can be bypassed using stacked VLAN0 and LLC/SNAP headers

Vulnerability Description

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.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

The following person or organization is credited with identifying this vulnerability, as recorded in the NVD database:

  • Etienne Champetier (@champtar) <champetier.etienne@gmail.com>

References

More from IEEE

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CVE-2021-27861
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CVE-2017-13097
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CVE-2017-13096
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CVE-2017-13095
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Affected Vendor

Affected Software

802.2, draft-ietf-v6ops-ra-guard, P802.1Q
Vulnerable Versions:
802.2h-1997, 08, D1.0

Timeline

Official Publish: September 27th, 2022
Last Modified: November 4th, 2025
Added to House: July 21st, 2026

CVSS Vectors

No vector data available

Weaknesses (CWE)

CWE-290

MITRE ATT&CK TTPs

T1557 Adversary-in-the-Middle
Collection
T1078 Valid Accounts
Persistence
T1550 Use Alternate Authentication Material
Defense Evasion
T1021 Remote Services
Lateral Movement
T1190 Exploit Public-Facing Application
Initial Access