Title
CVE-2021-27861: CISCO
Tags
CISCO, IOS
CVE
CVE-2021-27861
NVD 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)
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-2021-27861
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:
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
References:
https://standards.ieee.org/ieee/802.1Q/10323/
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/
https://kb.cert.org/vuls/id/855201
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