PT-2022-4863 · Cisco · Cisco Ios+1

Etienne Champetier · Published 2022-09-27 · Updated 2022-11-16 · CVE-2021-27853

Positive Technologies (AI Summary)

CVSS v3.1

4.7

Medium

Base vector

AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

Name of the Vulnerable Software and Affected Versions No specific software or versions are mentioned in the provided descriptions.

Description The issue is related to the implementation of the Ethernet encapsulation protocol, specifically concerning the combination of headers. This could allow a remote attacker to cause a denial of service or implement a man-in-the-middle (MITM) attack. 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.

Recommendations At the moment, there is no information about a newer version that contains a fix for this vulnerability.

Exploit

DoS

Authentication Bypass by Spoofing

Weakness Enumeration

CWE-290

Related Identifiers

BDU:2022-05987

CVE-2021-27853

Affected Products

Cisco Ios

Cisco Nexus

References · 12

• 🔥 https://blog.champtar.fr/VLAN0_LLC_SNAP · Exploit
• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-VU855201-J3z8CKTX · Vendor Advisory
• https://standards.ieee.org/ieee/802.1Q/10323 · Vendor Advisory
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-VU855201-J3z8CKTX · Vendor Advisory
• https://standards.ieee.org/ieee/802.2/1048 · Vendor Advisory
• https://osv.dev/vulnerability/CVE-2021-27853 · Vendor Advisory
• https://bdu.fstec.ru/vul/2022-05987 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2021-27853 · Security Note
• https://t.me/true_secator/3491 · Telegram Post
• https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08 · Note
• https://kb.cert.org/vuls/id/855201 · Note
• https://t.me/cibsecurity/50534 · Telegram Post