CVE-2021-27853 : Security Advisory and Response

A detailed overview of the vulnerability related to bypassing Layer 2 network filtering using stacked VLAN0 and LLC/SNAP headers.

Understanding CVE-2021-27853

This section will cover what CVE-2021-27853 is, the impact it carries, technical details, and mitigation measures.

What is CVE-2021-27853?

CVE-2021-27853 highlights a vulnerability that enables the bypassing of Layer 2 network filtering mechanisms like IPv6 RA guard or ARP inspection using VLAN 0 headers and LLC/SNAP headers.

The Impact of CVE-2021-27853

The exploit allows threat actors to evade security controls meant to safeguard Layer 2 network traffic, potentially leading to unauthorized network access and data breaches.

Technical Details of CVE-2021-27853

This section dives into the specific aspects of the vulnerability.

Vulnerability Description

The flaw lies in the ability to manipulate VLAN 0 and LLC/SNAP headers to circumvent established Layer 2 network safeguards.

Affected Systems and Versions

The vulnerability affects IEEE 802.2 (version 802.2h-1997), IETF draft-ietf-v6ops-ra-guard (version 08), and IETF P802.1Q (version D1.0).

Exploitation Mechanism

Threat actors can exploit this vulnerability by using specific combinations of VLAN 0 headers and LLC/SNAP headers to bypass network filtering controls.

Mitigation and Prevention

Learn how to protect your systems and networks from CVE-2021-27853.

Immediate Steps to Take

Organizations are advised to implement alternative network filtering mechanisms and stay updated on vendor security advisories.

Long-Term Security Practices

Long-term measures include regular security assessments, awareness training, and timely patch management.

Patching and Updates

Vendors may release patches or updates to address the vulnerability. Stay informed via vendor advisories and security bulletins.