CVE-2026-73443

Summary

On affected platforms running Arista EOS with VRRPv2 IP-AH authentication configured, an unauthenticated attacker within the same layer 2 network segment on which VRRP is running can capture a legitimate authenticated VRRP advertisement and replay it indefinitely. Replayed advertisements can be used to advertise stale VRRP state, for example to prevent a backup router from taking over the virtual gateway after the original master has gone down, resulting in a denial of service for hosts using the virtual gateway address.

Affected Software

VendorProductVersion RangeStatus
Arista NetworksEOS4.36.0 <= 4.36.1Faffected
Arista NetworksEOS4.35.0 <= 4.35.5Maffected
Arista NetworksEOS4.34.0 <= 4.34.7Maffected
Arista NetworksEOS4.33.0 <= 4.33.9Maffected

Weaknesses

  • CWE-294: CWE-294 Authentication Bypass by Capture-replay

Workarounds

Exposure is limited to attackers with access to the layer 2 network segment on which VRRP is running. Restricting physical and logical access to VRRP-enabled segments (for example with port security and by not extending VRRP VLANs to untrusted access ports) reduces the attack surface. Additionally, migrating virtual routers from VRRP version 2 with authentication to VRRP version 3 removes the vulnerable code path.

The below configuration shows how to configure VRRPv3 on VLAN 20:

switch(config)# interface vlan 20 switch(config-if-vl20)# vrrp 1 ipv4 version 3

References