Medium severity4.7NVD Advisory· Published Sep 27, 2022· Updated Jun 17, 2026

CVE-2021-27861

Description

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

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

Affected products

Ieee/Ieee 802.2
cpe:2.3:a:ieee:ieee_802.2:*:*:*:*:*:*:*:*
Range: <=802.2h-1997
Ietf/P802.1q2 versions
cpe:2.3:a:ietf:p802.1q:*:*:*:*:*:*:*:*+ 1 more
- cpe:2.3:a:ietf:p802.1q:*:*:*:*:*:*:*:*range: <=d1.0
- (no CPE)range: D1.0
IEEE/802.2v5
Range: 802.2h-1997
IETF/draft-ietf-v6ops-ra-guardv5
Range: 08

Patches

Vulnerability mechanics

References

datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/nvdThird Party Advisory
standards.ieee.org/ieee/802.1Q/10323/nvdThird Party Advisory
standards.ieee.org/ieee/802.2/1048/nvdThird Party Advisory
blog.champtar.fr/VLAN0_LLC_SNAP/nvd
kb.cert.org/vuls/id/855201nvd
www.kb.cert.org/vuls/id/855201nvd

News mentions

No linked articles in our index yet.

cvss	0.306
epss	0.000
exploit	0.000
kev	0.000
patch	0.000
ransomware	0.000