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CVE-2021-27854

20
FAUCET Score

CVE-2021-27854 describes a vulnerability in IEEE 802.1Q and 802.2 standards that allows Layer 2 network filtering, specifically IPv6 RA guard, to be bypassed through techniques like VLAN 0 headers and frame conversions between Ethernet and Wi-Fi. This medium-severity vulnerability (CVSS 4.7) has a low attack complexity and requires adjacent network access, potentially leading to information disclosure or denial of service, as highlighted by media coverage. While there are no known active exploits or public exploit code (Metasploit, Nuclei, ExploitDB), the vulnerability has garnered some community discussion and media attention.

Impacted Technologies

VendorProductVersion(s)CPE
<= 802.2h-1997CPE matchmatch criteria
cpe:2.3:a:ieee:ieee_802.2:*:*:*:*:*:*:*:*
<= d1.0CPE matchmatch criteria
cpe:2.3:a:ietf:p802.1q:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

4.7MEDIUM

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

Attack Vector
ADJACENT_NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
NONE
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.66%
Probability of exploitation in next 30 days
EPSS Percentile
48.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0066 is in the 75th percentile among its peer group of 1,802 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Advisories (1)

redhatCVE-2021-27854Moderate

kernel: layer 2 network filtering capabilities bypass / wifi

Sep 27, 2021

References

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