This advisory documents the impact of an internally found vulnerability in Arista EOS for security ACL bypass. The impact of this vulnerability is that the security ACL drop rule might be bypassed if a NAT ACL rule filter with permit action matches the packet flow. This could allow a host with an IP address in a range that matches the range allowed by a NAT ACL and a range denied by a Security ACL to be forwarded incorrectly as it should have been denied by the Security ACL. This can enable an ACL bypass.
The recommended resolution is to upgrade to a remediated software version at your earliest convenience. The fixed versions for the currently supported release trains are as follows: 4.24.10 and later releases in the 4.24.x train 4.25.9 and later releases in the 4.25.x train 4.26.6 and later releases in the 4.26.x train 4.27.4 and later releases in the 4.27.x train 4.28.0 and later releases in the 4.28.x train
Configure a NAT “drop” ACL rule for each security ACL “drop” rule that should be applied to the interface that has NAT configured. This will prevent the packets from being translated at the expense of maintaining the configuration in two places.
| Product | Vulnerable range | Fixed version | Advisory |
|---|---|---|---|
| Arista Networks EOS | >=4.24.0<=4.24.9 | 4.24.9 | advisory ↗ |
| Arista Networks EOS | >=4.25.0<=4.25.8 | 4.25.8 | advisory ↗ |
| Arista Networks EOS | >=4.26.0<=4.26.5 | 4.26.5 | advisory ↗ |
| Arista Networks EOS | >=4.27.0<=4.27.3 | 4.27.3 | advisory ↗ |