CVE-2021-27853: CISCO

Title

CVE-2021-27853 - CISCO

Tags

CISCO, IOS

CVE

CVE-2021-27853

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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

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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.

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Command Instructions:

COMMAND:

show version

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STDOUT:

Cisco IOS Software

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COMMAND:

show version

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STDOUT:

IE-2[0-9]{3}U

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COMMAND:

show version

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STDOUT:

WS-C65[0-9]{2}

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COMMAND:

show version

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STDOUT:

WS-C68[0-9]{2}

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COMMAND:

show version

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STDOUT:

WS-C3650-[0-9]{1,2}

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COMMAND:

show version

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STDOUT:

WS-C3850-[0-9]{2}

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COMMAND:

show version

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STDOUT:

C9200[d]

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COMMAND:

show version

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STDOUT:

C9300[d]

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COMMAND:

show version

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STDOUT:

C9400[d]

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COMMAND:

show version

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STDOUT:

C9500[d]

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COMMAND:

show version

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STDOUT:

C9600[d]

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Affected Versions:

15.5(01.01.85)SY07

15.2(07)E02

15.2(07)E03

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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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