CVE-2021-27853 L2 network filtering can be bypassed using stacked VLAN0 and LLC/SNAP headers
Attackers can bypass Layer 2 network filtering mechanisms like IPv6 RA guard or ARP inspection by using stacked VLAN0 and LLC/SNAP 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-2021-27853?
CVE-2021-27853 is a medium-severity vulnerability in Cisco Ios Xe, 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 or ARP inspection can be bypassed using combinations of VLAN 0 headers and LLC/SNAP headers.
Weakness: CWE-290
Which versions are affected by CVE-2021-27853?
It affects 96 products.
Products include Cisco Catalyst 6503-E Firmware, Cisco Catalyst 6504-E Firmware, Cisco Catalyst 6506-E Firmware, Cisco Catalyst 6509-E Firmware, Cisco Catalyst 6509-Neb-a Firmware, Cisco Catalyst 6509-v-E Firmware and 90 more.
How do I fix CVE-2021-27853?
No fix has been published for CVE-2021-27853 yet. Limit exposure of the affected software until one is available.
Is CVE-2021-27853 being exploited?
There is no known exploitation of CVE-2021-27853 in the wild and no public exploit code.
Sources
Also known as GHSA-v8jg-p3fp-g968.