Vulnerability · Published Sep 27, 2022 · Assigned by certcc
CVE-2021-27853L2 network filtering can be bypassed using stacked VLAN0 and LLC/SNAP headers
Medium 4.7
In plain English
A medium-severity authentication bypass by spoofing in 802.2 from IEEE. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 57% of all known vulnerabilities).
Severity (CVSS 3.1)4.7Medium
Exploit odds (30 days)0.8%top 42.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
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.
Affected products (as reported)
Weakness: CWE-290 · Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
References
- https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/
- https://standards.ieee.org/ieee/802.2/1048/
- https://standards.ieee.org/ieee/802.1Q/10323/
- 20220927 Vulnerabilities in Layer 2 Network Security Controls Affecting Cisco Products: September 2022 vendor-advisory
- https://kb.cert.org/vuls/id/855201
- https://blog.champtar.fr/VLAN0_LLC_SNAP/
- https://www.kb.cert.org/vuls/id/855201