Medium severity · published Sep 27, 2022
CVE-2021-27853
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
4.7
CVSS
0.8%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
Attack vector
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.8% · higher than 57% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
IX
IOS XE · Cisco
17.3.3 · source: NVD
C6
Catalyst 6503-e Firmware · Cisco
15.5(01.01.85)sy07 · source: NVD
C6
Catalyst 6504-e Firmware · Cisco
15.5(01.01.85)sy07 · source: NVD
C6
Catalyst 6506-e Firmware · Cisco
15.5(01.01.85)sy07 · source: NVD
C6
Catalyst 6509-e Firmware · Cisco
15.5(01.01.85)sy07 · source: NVD
C6
Catalyst 6509-neb-a Firmware · Cisco
15.5(01.01.85)sy07 · source: NVD
C6
Catalyst 6509-v-e Firmware · Cisco
15.5(01.01.85)sy07 · source: NVD
C6
Catalyst 6513-e Firmware · Cisco
15.5(01.01.85)sy07 · source: NVD
C6
Catalyst 6800ia Firmware · Cisco
15.5(01.01.85)sy07 · source: NVD
C6
Catalyst 6807-xl Firmware · Cisco
15.5(01.01.85)sy07 · source: NVD
C6
Catalyst 6840-x Firmware · Cisco
15.5(01.01.85)sy07 · source: NVD
C6
Catalyst 6880-x Firmware · Cisco
15.5(01.01.85)sy07 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-27853
CVE.org
https://www.cve.org/CVERecord?id=CVE-2021-27853
Exploit
https://blog.champtar.fr/VLAN0_LLC_SNAP/
Technical Description
https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/
Third Party Advisory
https://kb.cert.org/vuls/id/855201
Vendor Advisory
https://standards.ieee.org/ieee/802.1Q/10323/
Vendor Advisory
https://standards.ieee.org/ieee/802.2/1048/
Third Party Advisory
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-VU855201-J3z8CKTX
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