Title
CVE-2021-27853 - CISCO
Tags
CISCO, IOS
CVE
CVE-2021-27853
NVD Description
Layer 2 network filtering capabilities such as IPv6 RA guard or ARP inspection can be bypassed using combinations of VLAN 0headers and LLC/SNAP headers.
Exploit Available
True
Abused by Malware
False
You can find more insights and intelligence on this CVE at: https://vi.loginsoft.com/app/cve/CVE-2021-27853
Vulnerable Condition
To ascertain the vulnerable conditions and product versions deemed affected, issue the following commands and look for its associated as stated. If one more conditions matches then we can consider it as affected.
Command Instructions:
COMMAND:
show version
STDOUT:
Cisco IOS Software
COMMAND:
show version
STDOUT:
IE-2[0-9]{3}U
COMMAND:
show version
STDOUT:
WS-C65[0-9]{2}
COMMAND:
show version
STDOUT:
WS-C68[0-9]{2}
COMMAND:
show version
STDOUT:
WS-C3650-[0-9]{1,2}
COMMAND:
show version
STDOUT:
WS-C3850-[0-9]{2}
COMMAND:
show version
STDOUT:
C9200[d]
COMMAND:
show version
STDOUT:
C9300[d]
COMMAND:
show version
STDOUT:
C9400[d]
COMMAND:
show version
STDOUT:
C9500[d]
COMMAND:
show version
STDOUT:
C9600[d]
Affected Versions:
15.5(01.01.85)SY07
15.2(07)E02
15.2(07)E03
References:
https://standards.ieee.org/ieee/802.1Q/10323/
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-VU855201-J3z8CKTX
https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/
https://standards.ieee.org/ieee/802.2/1048/
https://blog.champtar.fr/VLAN0_LLC_SNAP/
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