MEDIUM
CVE-2021-27853
CWE-290Published: September 27, 2022· Updated: Jun 17, 2026
4.7
CVSS v3.1
Official 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.
Technical Analysis
CVE-2021-27853 requires adjacent network access, limiting remote exploitation but still posing risk in shared or local network environments.
The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.
The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.
CVSS v3.1 Vector Breakdown
Exploitability
Attack VectorAdjacent
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeChanged
Impact
ConfidentialityNone
IntegrityLow
AvailabilityNone
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
Affected Vendors & Products
Cisco306 product(s)
catalyst 6503-e firmwarecatalyst 6503-ecatalyst 6504-e firmwarecatalyst 6504-ecatalyst 6506-e firmwarecatalyst 6506-ecatalyst 6509-e firmwarecatalyst 6509-ecatalyst 6509-neb-a firmwarecatalyst 6509-neb-acatalyst 6509-v-e firmwarecatalyst 6509-v-e+294
ieee1 product(s)
ieee 802.2
ietf1 product(s)
p802.1q
Source: NVD CPE · 312 total CPE entries
Exploit & PoC Resources
NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.
Official Patches & Advisories
All References (13)
→
https://blog.champtar.fr/VLAN0_LLC_SNAP/Exploit · Third Party Advisory
→
https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/Technical Description · Third Party Advisory
→
https://kb.cert.org/vuls/id/855201Third Party Advisory · US Government Resource
→
https://standards.ieee.org/ieee/802.1Q/10323/Vendor Advisory
→
https://standards.ieee.org/ieee/802.2/1048/Vendor Advisory
→
→
https://blog.champtar.fr/VLAN0_LLC_SNAP/Exploit · Third Party Advisory
→
https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/Technical Description · Third Party Advisory
→
https://kb.cert.org/vuls/id/855201Third Party Advisory · US Government Resource
→
https://standards.ieee.org/ieee/802.1Q/10323/Vendor Advisory
→
https://standards.ieee.org/ieee/802.2/1048/Vendor Advisory
→
Quick Facts
CVE IDCVE-2021-27853
CVSS Score4.7 / 10
SeverityMEDIUM
WeaknessCWE-290
CISA KEVNo
Affected3 vendor(s)
PublishedSep 27, 2022
Related CVEs (CWE-290)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-27853 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.