CVE-2021-27861 L2 network filtering bypass using stacked VLAN0 and LLC/SNAP headers with invalid lengths
Attackers can bypass Layer 2 network filtering and IPv6 RA guard by crafting packets with invalid LLC/SNAP header lengths and optional VLAN0 headers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2021-27861?
CVE-2021-27861 is a medium-severity vulnerability in IEEE 802.2, published on 27 Sep 2022. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)
Which versions are affected by CVE-2021-27861?
It affects 2 products.
Products include Ieee Ieee 802.2, Ietf P802.1q.
How do I fix CVE-2021-27861?
No fix has been published for CVE-2021-27861 yet. Limit exposure of the affected software until one is available.
Is CVE-2021-27861 being exploited?
There is no known exploitation of CVE-2021-27861 in the wild and no public exploit code.
Other vulnerabilities in IEEE 802.2
Sources
Also known as GHSA-wcc2-hc4j-m2wc.