CVE-2021-27861
L2 network filtering bypass using stacked VLAN0 and LLC/SNAP headers with invalid lengths
Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)
Attack profile
How easy it is to exploit
- Attack vector
- Adjacent network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)
- Record
CVE-2021-27861- CVSS 3.1
- 4.7 Medium
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N - Weakness
- CWE-130, CWE-290
- Updated
- 2026-11-02
CVE List
L2 network filtering bypass using stacked VLAN0 and LLC/SNAP headers with invalid lengths
Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)
- Record
CVE-2021-27861- CVSS 3.1
- 4.7 Medium
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N - Weakness
- CWE-130, CWE-290
- Updated
- 2026-11-02
EUVDEUVD-2021-14599
Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)
- Record
EUVD-2021-14599- CVSS 3.1
- 4.7 Medium
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-wcc2-hc4j-m2wc
Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP...
Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)
- Record
GHSA-wcc2-hc4j-m2wc- CVSS 3.1
- 4.7 Medium
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N - Weakness
- CWE-130, CWE-290
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-27861 is a medium vulnerability (CVSS 4.7) in Ieee 802.2, published September 27, 2022. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.66%, the 51st percentile. No source names a fixed version.