CVE-2021-27861

Vulnerability Summary

On September 27, 2022, the following vulnerabilities affecting Cisco products were disclosed by Cert/CC as part of VU855201, titled L2 network security controls can be bypassed using VLAN 0 stacking and/or 802.3 headers: CVE-2021-27853: Layer 2 network filtering capabilities such as IPv6 RA guard or ARP inspection can be bypassed using a combination of VLAN 0 headers and LLC/SNAP headers. CVE-2021-27854: Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using a combination of VLAN 0 headers, LLC/SNAP headers in Ethernet to Wifi frame translation, and in the reverse-Wifi to Ethernet. CVE-2021-27861: Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers). CVE-2021-27862: Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length and Ethernet to Wifi frame conversion (and optionally VLAN0 headers). Exploitation of these vulnerabilities could allow an adjacent malicious user to bypass configured first-hop security (FHS) features on the affected Cisco products. For more information about these vulnerabilities, see the Details section of this advisory. This advisory is available at the following link: sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-VU855201-J3z8CKTX

Vulnerability Trend

Vendor Advisories

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