PT-2022-9877 · Cisco · Cisco Ios+2

Published 2022-09-27 · Updated 2022-10-12 · CVE-2021-27861

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 allows Layer 2 network filtering capabilities, such as IPv6 RA guard, to be bypassed. This can be achieved by using LLC/SNAP headers with invalid length, and optionally, VLAN0 headers. There is no information provided about the estimated number of potentially affected devices or real-world incidents where this issue was exploited.

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

DoS

Authentication Bypass by Spoofing

Weakness Enumeration

CWE-130

CWE-290

Related Identifiers

CVE-2021-27861

Affected Products

Cisco Ios

Cisco Ios Xr

Cisco Nexus

References · 10

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-VU855201-J3z8CKTX · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2021-27861 · Security Note
• https://osv.dev/vulnerability/CVE-2021-27861 · Vendor Advisory
• https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08 · Note
• https://blog.champtar.fr/VLAN0_LLC_SNAP · Note
• https://kb.cert.org/vuls/id/855201 · Note
• https://standards.ieee.org/ieee/802.2/1048 · Note
• https://t.me/true_secator/3491 · Telegram Post
• https://t.me/cibsecurity/50533 · Telegram Post
• https://standards.ieee.org/ieee/802.1Q/10323 · Note